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MALL   BOAT 
NAVIGATION 


By  F.  W,  STERIJNO 


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SMALL  BOAT  NAVIGATION 


SMALL  BOAT 
NAVIGATION 


BY 
LIEUT.  COM.  F.  W.  STERONG 

U.  S.  NAVY  (RETIRED) 


*♦»»••*     » 


THE  MACMILLAN  COMPANY 
1942 


.'Si 


REPLACING 

COPTBIOHT,   1917, 

Bt  the  Macmillan  company 

All  rights  reserved — no  part  of  this  book  may  be 
reproduced  in  any  form  without  permission  in  writing 
from  the  publisher,  except  by  a  reviewer  who  wishes 
to  quote  brief  passages  in  connection  with  a  review 
written    for    inclusion    in    magazine    or    newspaper. 


ii*:r:--i*!::    :  - 


TrifiUd  in  the  United  States  of  America  by 

THK   PEBBI8    PBINTmO    COMPANY,    NEW    TOBK 


CONTENTS 

PART  I 
NAVIGATION 

CHAPTER  PAGE 

I     Navigation ^ 

II     Navigational  Instruments,  Books,  Rec- 
ords, Etc 14 

III     The  Vessel's  Position 44 

IV     Dead  Reckoning  .......     75 

PART  II 
SEAMANSHIP 

V     Soundings,  Tides,  Etc 97 

VI     Light  and  Buoy  System  of  the  United 

States 110 

VII     Weather 118 

VIII     Rules  op  the  Road 180 


M168705 


PART  I 
NAVIGATION 


SMALL  BOAT  NAVIGATION 


CHAPTER  I 

NAVIGATION 

NAVIGATION  is  that  science  which  affords 
the  knowledge  necessary  to  conduct  a  ves- 
sel from  one  point  to  another  on  the  earth 
and  provides  a  means  of  determining  the  position 
of  the  vessel  at  any  time.  There  are  three  gen- 
eral branches  to  this  science,  viz : 

(1)  PHoting. 

(2)  Dead  Reckoning. 
(S)  Nautical  Astronomy, 

PUotmg  is  determining  the  position  of  a  vessel 
by  observations  on  known  visible  charted  objects, 
or  by  soundings  of  the  depth  of  the  sea. 

Dead  Reckoning,  or  the  method  of  sailings,  is 
a  means  of  deducing  a  vessel's  position  from  the 
direction  and  distance  sailed  from  a  previous 
known  position.  This  method  involves  the  rules 
of  plane  trigonometry. 

Nautical  Astronomy  treats  of  the  determina- 
tion of  a  vessel's  position  by  observation  of  celes- 

9 


Yd  "SMALL  BOAT  NAVIGATION 

tial  bodies  —  the  sun,  stars,  moon,  and  planets. 
It  is  based  on  spherical  trigonometry  and  its  use  is 
principally  confined  to  deep  sea  navigation.  On 
this  account  it  is  not  dealt  with  in  this  work. 

UNITS  DEFINED 

The  Statute  Mile,  which  is  5,280  feet,  is  em- 
ployed in  land  measurements.  It  is  used  to  some 
extent  in  navigating  river  and  lake  vessels,  espe- 
cially on  the  Great  Lakes,  but  by  far  the  more 
commonly  used  unit  is 

The  Geographical  or  Nautical  Mile,  This  unit 
of  linear  measurement,  used  by  navigators,  is  gen- 
erally termed  the  nautical  or  sea  mile.  It  is  ap- 
proximately 6,080  feet.  It  has  various  values  as 
defined  by  the  standards  of  different  countries, 
but  from  the  navigator's  standpoint  these  various 
standards  do  not  vary  materially  from  the  above 
value.  Jt  is  equal  to  a  minute  of  arc  of  the  equa- 
tor, "^For  purposes  of  navigation  the  nautical 
mile  is  assumed  equal  to  a  minute  of  latitude  at 
all  points  of  the  earth.  Hence,  when  a  vessel 
changes  her  position  to  the  north  or  south  by  one 
nautical  mile,  it  is  assumed  that  the  latitude  has 
changed  1'.  Owing  to  the  fact  that  the  meridi- 
ans converge  toward  the  poles,  the  difference  in 
longitude  due  to  a  change  of  position  of  one  mile 
to    the   east    or   west   varies   with   the   latitude. 


NAVIGATION  ii 

Whereas  a  departure  (change  of  position  to  east 
or  west)  of  1  mile  at  the  equator  equals  1'  of  arc, 
the  same  departure  of  1  mile  in  a  latitude  of  60° 
amounts  to  9f  in  longitude. 

The  Knot  is  the  measure  of  speed  and  equals 
one  nautical  mile  per  hour. 

The  Axis  of  the  Earth  is  a  diameter  passing 
through  the  poles  of  the  .earth  and  about  which 
the  earth  revolves. 

The  Terrestrial  Equator  is  a  great  circle  of  the 
earth  passing  through  the  middle  point  of  this 
axis  and  perpendicular  thereto.  It  divides  the 
earth  into  the  Northern  and  Southern  hemi- 
spheres, and  every  point  on  this  equator  is  equi- 
distant from  the  poles.  Longitude  is  measured 
along  the  equator. 

Terrestrial  Meridians  are  great  circles  of  the 
earth  passing  through  the  poles.  They  are  per- 
pendicular to  the  equator.  Latitude  is  measured 
on  the  meridians,  being  0°  at  the  equator  and  90° 
at  the  poles.  The  Meridian  of  a  place  is  that 
meridian  passing  through  the  place. 

The  Prime  Meridian  is  that  meridian  from 
which  longitude  is  measured.  The  meridian 
passing  through  Greenwich,  England,  is  almost  \^ 

universally  accepted  as  the  prime  meridian  for 
navigation.  Longitude  is  measured  from  0°  at 
Greenwich,  East  and  West  to  180°. 


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12    SMALL  BOAT  NAVIGATION 

Parallels  af  Latitude  are  small  circles  of  the 
earth  parallel  to  the  equator. 

The  Latitude  of  a  place  is  the  arc  of  the  merid- 
ian intercepted  between  the  equator  and  that 
place.  It  is  reckoned  north  and  south  from  the 
equator  as  an  origin,  up  to  90°  at  the  poles. 

The  Longitude  of  a  place  is  the  arc  of  the  equa- 
tor intercepted  between  the  meridian  of  the  place 
and  the  prime  meridian.  Longitude  is  measured 
East  and  West  through  180°  from  the  meridian 
of  Greenwich. 

The  Difference  of  Latitude  of  two  places  is  the 
portion  of  a  meridian  included  between  the  two 
parallels  of  latitude  passing  through  the  two 
places.  When  two  places  are  on  the  same  side  of 
the  equator  the  difference  of  latitude  is  the  nu- 
merical difference  between  the  latitudes  of  the 
places ;  when  on  opposite  sides  of  the  equator  the 
difference  of  latitude  is  the  numerical  sum  of  the 
two  places.  The  difference  of  latitude  is  called 
North  or  South  to  indicate  in  which  direction  a 
vessel  would  sail  to  make  the  change. 

The  Difference  of  Longitude  of  two  places  is  the 
arc  on  the  equator  intercepted  between  the  meridi- 
ans passing  through  the  two  places.  When  the 
places  are  in  the  same  longitude  (viz:  East  or 
West),  the  difference  of  longitude  is  the  numer- 
ical difference  between  the  longitudes  of  the  two 


NAVIGATION  13 

places ;  when  in  different  longitudes,  the  difference 
in  longitude  is  the  numerical  sum  of  the  two  longi- 
tudes, or  360°  minus  this  sum.  The  difference  of 
longitude  is  marked  East  or  West  to  denote  in 
which  direction  a  vessel  would  sail  to  make  the 
change. 


CHAPTER  II 

NAVIGATIONAL    INSTRUMENTS,    BOOKS,    RECORDS, 
ETC. 

1.    NAVIGATIONAL  INSTRUMENTS 

THE  following  instruments  are  indispensa- 
ble to  the  navigator  when  piloting:  (a)  di- 
viders or  compasses,  (b)  parallel  rulers, 
(c)  log,  chip  or  patent,  (d)  lead  and  line,  (e) 
compass,  liquid,  dry,  or  gyroscopic,  (f)  azimuth 
circle,  (g)  barometer,  mercurial  or  aneroid,  (h) 
thermometer.  A  sextant  and  protractor  may  also 
be  included  in  the  outfit,  although  the  former  is 
entirely  unnecessary, 

(a)  Dividers  (or  Compasses)  consist  of  two 
pointed  legs  movable  about  a  joint  so  that  the 
points  at  the  extremities  of  the  legs  may  be  set  at 
any  desired  distance  apart.  Dividers  is  an  in- 
strument used  for  measuring  distances  on  a  chart. 
One  of  the  pointed  extremities  can  be  replaced  by 
a  pencil  or  pen  for  describing  arcs  or  circles  and 
in  this  case  the  instrument  is  called  a  compass, 

(b)  Parallel  Rulers  consist  of  two  wooden 
straight  edges,  joined  by  two  metal  links,  so  con- 

14 


INSTRUMENTS,  BOOKS,  ETC.     15 

structed  that  in  all  positions  of  the  links  the 
straight  edges  are  always  parallel  to  each  other. 
It  is  used  to  draw  lines  parallel  to  each  other,  and 
especially  in  chart  work  for  transferring  lines  on 
the  chart  to  the  compass  rose,  ,for  laying  off 
courses  by  transferring  them  from  the  compass 
rose,  and  for  plotting  bearings  of  objects. 

(c)  The  Log  is  an  instrument  for  measuring 
or  estimating  the  speed  of  the  vessel  and  the  dis- 
tance run  for  any  given  period.  It  takes  a  va- 
riety of  forms  that  may  be  classified  under  two 
heads,  the  chip  log  (which  measures  the  speed  of 
the  vessel  at  any  instant)  and  the  patent  log 
(which  is  cumulative  and  measures  the  distance 
run  for  any  interval). 

The  Chip  Log,  which  is  quite  inexpensive  and 
can  be  made  by  the  navigator,  consists  of  three 
parts,  the  log-chip,  the  log-lme,  and  the  log-glass. 
Its  principle  is  that,  if  a  light  object  is  thrown 
from  the  ship,  it  ceases  to  partake  of  the  motion 
of  the  ship  as  soon  as  it  strikes  the  water.  If 
after  any  known  interval  of  time  its  distance  from 
the  ship  is  known  (this  being  equivalent  to  the 
distance  the  ship  has  travelled  in  the  known  in- 
terval of  time)  the  approximate  speed  of  the  ship 
can  be  computed. 

The  log-chip  is  a  thin  wooden  quadrant  of 
about  5''  radius,  the  circular  edge  being  weighted 


i6    SMALL  BOAT  NAVIGATION 

with  lead  so  that  the  chip  will  float  upright,  apex 
up.  The  log-line  is  knotted  into  a  hole  at  the 
apex.  The  ends  of  a  bight  of  line  are  knotted 
into  the  other  two  corners  of  the  chip.  Into  this 
bight  is   seized  a  wooden  peg  which  fits  into  a 


Fig.  1.— Chip  Log. 

«ocket  seized  on  the  log-line.  When  the  peg  is  in 
the  socket,  all  three  lines  to  the  corners  of  the  chip 
are  of  equal  length.  This  contrivance  facilitates 
hauling  in  the  chip  after  the  speed  is  obtained. 

The  log-line^  which  is  made  of  halyard  stuff,  is 
about  150  fathoms  long.  One  end  is  secured  to 
the  chip  and  the  other  to  a  reel  on  which  the  line 
is  wound.  The  line  is  marked  at  about  15  fath- 
oms from  the  chip  end  by  a  piece  of  bunting. 
This  part  of  the  line  is  called  stray  line.  From 
this  piece  of  bunting  the  line  is  marked  at  every 
47  feet  3  inches  by  a  piece  of  fish  line  held  between 
the  strands  of  the  log-line,  the  line  being  marked 
by  a  knot  in  the  fish  line  for  every  division  (47 
feet  3  inches)  from  the  bunting.     Thus  at  94  feet 


INSTRUMENTS,  BOOKS,  ETC.     17 

6  inches  from  the  bunting  the  piece  of  fish  line 
has  two  knots  in  it,  etc.  These  main  divisions, 
called  knots,  are  further  subdivided  into  five  equal 
parts  by  pieces  of  white  bunting ,  between  the 
strands  to  indicate  two-tenths  of  a  knot. 

The  log-glass  is  a  sand  glass  similar  to  an  hour 
glass  constructed  to  run  for  28.  seconds.  A  14j- 
second  glass  is  also  used. 

Three  men  are  needed  to  "  heave  the  log."  One 
heaves  the  chip-log  and  tends  the  log-line,  one 
holds  the  reel,  and  one  tends  the  log-glass. 

To  find  the  speed  by  the  chip-log,  hold  the  reel 
by  its  handles  and  unwind  some  of  the  stray  line. 
Insert  the  toggle  in  its  socket  and  heave  the  chip 
overboard,  allowing  the  line  to  run  out  freely. 
As  the  first  piece  of  bunting,  which  marks  the  end 
of  the  stray  line,  passes  over  the  rail  invert  the 
log-glass.  Just  as  the  last  particle  of  sand  passes 
from  the  top  to  the  bottom  of  the  glass  seize  the 
log-line,  which  has  been  running  out  freely.  The 
subdivisional  mark  which  is  now  at  the  rail  indi- 
cates the  speed  of  the  vessel  in  knots  and  tenths. 
For  instance,  if  the  cord  having  three  knots  is  at 
the  rail,  the  vessel  is  making  three  knots  per  hour. 
This  can  be  demonstrated  as  follows : 

Principle  of  Construction,  When  the  chip  hits 
the  water  it  ceases  to  partake  of  the  motion  of 
the  ship  and  becomes  stationary  in  the  water. 


1 8    SMALL  BOAT  NAVIGATION 

Between  the  first  mark  and  the  third  the  interval 
of  time  is  28  seconds  (the  time  it  takes  the  sand  to 
run  from  the  top  to  the  bottom  of  the  glass).  In 
this  interval  of  time  the  vessel  moves  3  times  4*7 
feet  3  inches  (as  shown  by  the  log-line).     Now  in 

feet   is   the   distance  that 

the  vessel  would  move  in  one  hour  at  the  same  rate. 

^       3X47.25X60X60      ^^ 

Or     =  3  knots  per  hour. 

28  X  6080 

The  28-second  glass  is  used  for  low  speeds.     For 

speeds  over  5  knots  a  14-second  glass  is  used  and 

the  reading  of  the  log-line  is  doubled. 

To  haul  in  the  line  after  a  reading  is  obtained, 
give  the  line  a  sharp  tug.  This  will  release  the 
toggle  and  the  chip  will  lay  flat  on  the  surface 
and  can  be  hauled  in  hand  over  hand  and  reeled 
up. 

The  whole  apparatus  should  be  overhauled  fre- 
quently to  check  the  log-line  markings  and  the  log- 
glass.  The  line  must  be  frequently  checked  and 
remarked  as  it  stretches  or  shrinks,  and  should 
be  marked  when  wet.  The  glass  is  checked  by 
comparing  it  with  a  watch,  and  the  sand  is  dried 
if  it  becomes  damp  as  indicated  by  requiring  more 
than  28  seconds  to  pass  from  the  top  to  the  bot- 
tom of  the  glass. 

Figure  1  shows  the  parts  of  the  chip-log  and 


INSTRUMENTS,  BOOKS,  ETC.     19 

the  necessary  dimensions  for  making  one  of  these 
instruments. 

In  lieu  of  the  log  glass  furnished  with  commer- 
cial outfits  time  may  be  kept  with  the  watch  and 
for  convenience  a  30-second  interval  may  be  sub- 
stituted for  the  28-second  interval  indicated  by 
the  log  glass.  In  this  case  the  knot  marks  on  the 
log  line  are  placed  50  feet  8  inches  apart. 

The  principle  of  marking  the  log  line  can  be 
checked  easily.  Suppose  the  vessel  is  moving  at 
the  rate  of  one  knot  (6080  feet  per  hour).  Then 
in  30  seconds  it  would  move  50  feet  8  inches. 
This  is  the  length  between  markings.  If  the  line 
is  accurately  marked  and  the  log  properly  con- 
structed the  speed  indicated  by  the  chip  log  will 
be  one  knot. 

The  Patent  Log  is  a  mechanical  contrivance  for 
measuring  the  actual  distance  that  a  vessel  travels 
through  the  water.  It  is  sometimes  called  a  taff- 
rail  log  because  it  is  usually  installed  on  the  taff- 
rail.  It  takes  a  variety  of  forms,  but  all  are 
more  or  less  subject  to  inaccuracies  and  all  em- 
body the  same  principles. 

The  patent  log  consists  of  three  parts,  (1)  the 
rotator,  a  conical  shaped  piece  of  brass  fitted  with 
vanes  which  is  towed  astern  and  caused  to  rotate 
as  it  passes  through  the  water  at  a  speed  propor- 
tionate to  the  speed  of  the  vessel;  (2)  a  register , 


20    SMALL  BOAT  NAVIGATION 

located  on  the  vessel's  rail.     This  register  is  con- 
nected to  the  rotator  by  a  line  which  communi- 


FiG.  2.— NegTis  Taffrail  Log. 


cates  the  revolutions  of  the  rotator  to  cyclometer 
gear  in  the  register.     The  whole  is  so  calibrated 


INSTRUMENTS,  BOOKS,  ETC.    21 

that  the  miles  and  tenths  run  by  the  vessel  are  reg- 
istered bj  appropriate  dials  on  the  register;  (3) 
the  line,  which  is  specially  made.  Usually  about 
400  feet  of  line  is  used  to  connect*  the  rotator 
and  the  register.  A  high  speed  requires  a  longer 
line  than  a  low  speed.  The  parts  of  the  Negus 
Taffrail  Log  are  shown  in  Figure  2. 

Patent  logs  are  not  exact  instruments  and 
many  inaccuracies  enter  even  when  in  good  work- 
ing order.  They  must  be  carefully  watched.  If 
correct  at  one  speed  they  may  be  inaccurate  at  a 
faster  or  slower  speed;  they  register  differently 
in  a  head  and  a  following  sea,  and  in  smooth  and 
rough  weather.  The  error  of  the  patent  log 
should  be  determined  for  varying  conditions  of 
sea  and  at  different  speeds  for  every  run  between 
two  ports,  if  the  speed  is  not  affected  by  tide,  and 
a  record  of  errors  under  these  varying  conditions 
should  be  kept  to  correct  future  readings. 

The  revolutions  of  the  screw  propeller  afford 
the  most  accurate  measure  of  the  speed  of  a  vessel 
and  the  distance  steamed.  The  revolutions  of  the 
propeller  (engine  speed)  can  be  obtained  by  a 
small  instrument  called  a  tachometer.  By  run- 
ning over  a  measured  mile  (or  other  known  dis- 
tance) at  various  engine  speeds,  the  revolutions 
corresponding  to  various  speeds  can  be  obtained 
and  tabulated  thus : 


22    SMALL  BOAT  NAVIGATION 

Revolutions  Speed  in  Knots 


85 

7 

97 

8 

110 

9 

125 

10 

142 

11 

160 

12      etc. 

Entering  this  table  with  the  average  revolutions 
for  any  interval  of  time,  the  corresponding  speed 
can  be  obtained.  While  this  is  the  most  accurate 
method  of  getting  the  speed,  it  must  be  borne  in 
mind  that  by  whatever  of  the  above  methods  the 
speed  is  obtained,  it  is  the  speed  through  the 
water  and  that  to  obtain  the  speed  made  good 
over  the  ground  allowances  must  be  made  for  the 
local  current. 

(d)  The  Lead  and  Line  is  a  device  for  ascer- 
taining the  depth  of  water.  It  consists  of  a  suit- 
ably marked  line,  having  a  long  hexagonal  or  oc- 
tagonal lead  at  its  end.  Two  sizes  of  leads  are 
used,  one  weighing  from  7  to  14  pounds,  called  the 
hand  lead,  and  used  for  depths  up  to  25  fathoms, 
and  the  other  weighing  from  30  to  100  pounds, 
called  the  deep  sea  lead,  and  used  for  depths  over 
25  fathoms. 

Lead  lines  are  marked,  measuring  from  the  bot- 
tom of  the  lead  secured  to  the  line,  as  follows : 


INSTRUMENTS,  BOOKS,  ETC.    23 

At    2  fathoms  with  two  leather  strips, 
3  fathoms  with  three  leather  stripg, 
5  fathoms  with  a  white  rag, 
7  fathoms  with  a  red  rag, 

10  fathoms  with  a  leather  having  a  hole  in  it, 

13  fathoms  the  same  as  3, 

15  fathoms  the  same  as  5, 

17  fathoms  the  same  as  7, 

90  fathoms  with  two  knots, 

95  fathoms  with  one  knot, 

30  fathoms  with  three  knots, 

35  fathoms  with  one  knot,  etc. 

Sometimes  the  lead  is  marked  in  feet  around 
the  depth  corresponding  to  the  vessel's  draft. 
Soundings  that  correspond  to  depths  marked  on 
the  lead  line  are  called  "  marks  ";  intermediate 
soundings  are  called  "  deeps,**  Lead  lines  should 
be  marked  when  wet,  and  should  frequently  be 
verified  and  remarked  when  necessary.  The  bot- 
tom of  the  deep  sea  lead  is  hollow.  When  taking 
a  sounding  this  cavity  is  filled  with  tallow  (called 
"  arming  the  lead  " )  which  picks  up  a  sample  of 
the  bottom.  This  allows  a  comparison  with  the 
character  of  the  bottom  as  indicated  on  the  chart. 

The  Sounding  Machine  is  an  instrument  for 
obtaining  rapid  soundings  at  great  depth.  It  is 
employed  on  all  large  ships  and  is  described  at 
length  in  Chapter  6. 

(e)  The  Compass  may  take  one  of  three 
forms,  liquid,  dry,  or  gyroscopic.  The  liquid 
compass  is  the  one  most  commonly  used  in  this 


24    SMALL  BOAT  NAVIGATION 

country  and  will  be  described  later.  The  dry  com- 
pass is  used  extensively  in  England.  The  gyro- 
scopic compass  is  used  in  the  U.  S.  Navy ;  its  high 
cost  precludes  its  use  in  any  but  the  largest  ships. 

The  Wet  Compass  consists  of  a  skeleton  card 
7%"  or  less  in  diameter,  made  of  tinned  brass,  rest- 
ing on  a  pivot  in  liquid,  with  provision  for  two 
pairs  of  magnets  symmetrically  placed.  The  mag- 
nets consist  of  four  cylindrical  bundles  of  steel 
wire  that  are  magnetized  as  bundles  between  the 
poles  of  an  electromagnet.  They  are  cased  in 
cylinders  and  secured  to  the  underside  of  the  com- 
pass card  in  a  direction  parallel  to  the  North  and 
South  markings  of  the  card. 

The  card  is  curved,  annular  shape  or  flat,  gradu- 
ated by  quarter  points,  and  a  card  circle  is  ad- 
justed to  its  outer  edge  graduated  to  half  degrees, 
with  readings  at  every  point  and  every  five  de- 
grees, as  seen  in  Figure  3. 

The  card  is  secured  on  a  concentric  spheroidal 
air  vessel  which  rests  on  liquid  in  the  compass 
bowl.  The  air  vessel  is  fitted  with  an  agate  bear- 
ing which  rests  on  a  pivot  in  the  compass  bowl, 
most  of  the  weight  of  the  card  being  supported 
by  the  liquid  and  only  a  slight  pressure  being  on 
the  pivot. 

The  compass  bowl  of  cast  bronze  has  a  glass 
cover  so  that  the  card  can  be  seen.     The  cover  is 


INSTRUMENTS,  BOOKS,  ETC.     25 

made  tight  by  a  rubber  gasket.  The  liquid  in 
the  bowl  is  45%  pure  alcohol  and  55%  distilled 
water.  The  inside  of  the  bowl  is  painted  white 
and  a  lubber's  point  is  drawn  in  the  bowl  in  the 


Pio.  3. —  Compass  Points. 

fore  and  aft  line  of  the  ship.     This  is  the  refer- 
ence point  when  reading  the  compass. 

The  under  side  of  the  bowl  constitutes  an  ex- 
pansion chamber  which  allows  for  expansion  with 
a  change  of  temperature  of  the  liquid  in  the  bowl. 


26    SMALL  BOAT  NAVIGATION 

The  bowl  is  mounted  by  double  gymbals  on  a  com- 
position stand.  This  stand  contains  magnets  to 
compensate  the  compass.  The  bowl  can  be  cov- 
ered by  a  spun  brass  hood  which  fits  on  the  stand 
and  can  be  revolved  for  taking  bearings. 

Boxing  the  Compass  is  the  process  of  naming 
the    points    in    their    order.     The    four    points, 


Fig.  4. —  Azimuth  Circle. 

North,  East,  South,  and  West,  are  called  cardmal 
points.  Midway  between  the  cardinal  points  are 
the  intercardinal  points,  N.E.,  S.E.,  S.W.,  N.W. 
The  names  of  all  points  are  shown  in  Figure  3. 

(f)  The  Azimuth  Circle  consists  of  a  com- 
position ring  which  fits  over  the  edge  of  the  com- 
pass bowl,  Figure  4*.  At  one  extremity  of  a  diam- 
eter is  a  curved  mirror  hinged  to  move  about  a 
horiiontal  axis,  and  facing  this,  at  the  other  ex- 


INSTRUMENTS,  BOOKS,  ETC.     27 

tremity  of  the  diameter,  is  a  cased  prism  which  has 
a  narrow  slit  in  the  case  facing  the  mirror.  This 
part  of  the  instrument  is  used  to  take  azimuths  of 
the  sun  for  compass  work. 

At  the  extremities  of  another  diameter  (at  right 
angles  to  the  first)  is  a  hinged  vertical  wire,  and  a 
hinged  plate  having  a  vertical  slit.  This  is  used 
for  taking  direct  bearings  of  an  object.  Hinged 
on  the  same  pivot  as  the  vertical  wire  is  a  smoked 
glass  reflector  for  azimuth  work  with  the  sun  or 
stars. 

A  level  on  the  azimuth  rim  shows  when  the  circle 
is  horizontal.  All  observations  must  be  taken 
with  a  horizontal  azimuth  circle. 

(g)  The  Barometee  is  an  instrument  for 
measuring  the  atmospheric  pressure.  Barometric 
observations  are  necessary  for  weather  predic- 
tions. Some  form  of  barometer  is  necessary  on  all 
vessels.  There  are  two  forms,  the  Mercurial  Ba- 
rometer, and  the  Aneroid  Barometer.  The  mer- 
curial barometer  is  carried  on  large  yachts. 
Smaller  boats  should  be  equipped  with  the  aneroid. 

The  Mercurial  Barometer  indicates  atmospheric 
pressure  by  the  height  of  a  column  of  mercury. 
If  a  glass  tube,  closed  at  one  end,  is  entirely  filled 
with  mercury  and  then  placed  open  end  down  over 
a  cup  of  mercury  (no  mercury  being  allowed  to  es- 
cape from  the  tube  during  the  operation)  the  mer- 


28    SMALL  BOAT  NAVIGATION 

cury  in  the  tube  will  fall  until  its  level  is  about  30 
inches  above  the  level  of  the  mercury  in  the  cup. 
This  column  of  mercury,  in  the  tube,  is  sustained 
by  the  pressure  of  air  on  the  mercury  in  the  cup, 
and  will  rise  or  fall  with  this  pressure  (which  is 
atmospheric  pressure). 

This  is  in  effect  a  barometer.  In  practice  the 
cup  and  tube  are  encased  in  a  brass  case,  cut 
away  near  the  level  of  mercury  in  the  tube ;  along 
this  opening  is  a  scale  for  reading  the  height  of 
mercury  in  inches,  a  twrnier  being  fitted  for  ac- 
curate readings. 

The  Vernier  is  an  attachment  used  on  many  in- 
struments, such  as  barometers,  sextants,  protrac- 
tors, etc.,  to  facilitate  exact  readings.  It  consists 
of  a  metal  scale,  similar  in  construction  to  that  of 
the  scale  to  which  it  is  fitted  and  arranged  to  move 
along  the  main  scale  by  a  rack  and  pinion. 

The  vernier  scale  has  a  total  length  equal  to  one 
of  the  whole  divisions  of  the  main  scale,  but  this 
length  is  divided  into  one  more  or  one  less  part 
than  the  number  of  subdivisions  into  which  the 
whole  division  of  the  main  scale  is  divided. 

Suppose  that  a  barometer  scale  is  divided  into 
tenths  of  an  inch  and  that  a  length  of  nine  such 
divisions  be  divided  into  ten  parts  for  a  vernier, 
Figure  5.  Number  the  vernier  divisions  from  0  at 
the  bottom  to  10  at  the  top.     If  the  bottom  divi- 


INSTRUMENTS,  BOOKS,  ETC.    29 


OP- 


^7. 


^-5a 


sion  of  the  vernier  is  brought  level  with  the  top  of 
the  mercurial  column  the  scale  is  read  as  follows: 
In  Figure  5  the  mercury  stands 
above  the  mark  29.6  on  the  main 
scale.  Find  the  division  of  the  ver- 
nier that  coincides  with  a  division 
of  the  main  scale.  In  the  figure 
this  division  is  "  1."  Therefore  .01 
must  be  added  and  the  exact  read- 
ing is  29.61. 

The  Aneroid  Barometer  is  an  in- 
strument by  which  the  atmospheric 
pressure  is  measured  bj  the  elastic- 
ity of  a  metal  plate.  It  consists  of 
a  cylindrical  brass  box,  the  metal 
being  very  thin.  This  box  is  in  a 
state  of  partial  vacuum.  As  the 
atmospheric  pressure  increases  the 
enclosed  air  is  compressed  and  the 
ends  of  the  box  approach  each  other. 
Suitable  levers  communicate  this 
motion  of  the  box  ends  to  a  pointer 
that  moves  over  a  suitable  scale. 
These  levers  magnify  the  motion  of 
the  box  ends  and  the  scale  is  cali- 
brated to  indicate  the  air  pressure. 

Barometer  Comparisons.  What- 
ever  the  form  of  barometer  used,  it       *  scale. 


-J19.S 


^za 


30    SMALL  BOAT  NAVIGATION 

will  be  subject  to  errors  due  to  derangements  or 
to  inaccurate  construction.  Because  of  this  it  is 
necessary  to  compare  the  barometer  frequently 
with  a  standard  of  known  error.  At  all  principal 
ports  a  standard  mercurial  barometer  is  available 
for  comparison.  From  this  comparison  the  ba- 
rometer error  can  be  computed  and  applied  to  fu- 
ture readings.  At  the  principal  ports  the  reading 
of  a  standard  barometer  at  specified  times  is  pub- 
lished in  the  daily  papers.  By  observing  the  ba- 
rometer on  board  at  the  same  time  the  error  of 
the  vessel's  instrument  is  obtained. 

(h)  The  Thermometer  is  an  instrument  for 
measuring  temperatures.  Its  principle  is  too  well 
known  to  require  discussion.  It  is  an  aid  to  the 
mariner  in  predicting  weather,  judging  the  humid- 
ity of  the  atmosphere,  and,  through  the  tempera- 
ture of  the  sea  water,  finding  proximity  of  cur- 
rents such  as  the  Gulf  Stream.  Sea  water  used  for 
observations  should  be  drawn  from  at  least  three 
feet  below  the  surface. 

The  Psychrometer  consists  of  two  thermome- 
ters called  the  wet  and  dry  hulhs.  The  dry-bulb 
thermometer  gives  the  temperature  of  the  air. 
The  wet-bulb  thermometer  is  exactly  like  the  dry- 
bulb  except  that  its  mercurial  bulb  is  surrounded 
with  cloth  which  is  kept  moist.  It  indicates  the 
temperature   of   evaporation.     By    reading   both 


INSTRUMENTS,  BOOKS,  ETC,    31 

bulbs  the  humidity  of  the  air  is  obtained  and  prob- 
ability of  rain  can  be  foretold. 

The  Sextant  ^  is  one  of  the  most  valuable  of 
deep  sea  navigational  instruments,  but  is  of  little 


Fio.  6.— Sextant 


use  when  coasting.  It  is  used  to  obtain  the  angle 
between  two  objects,  terrestrial  or  celestial,  by 
bringing  into  coincidence  at  the  observer's  eye  the 
rays  of  light  from  the  two  objects,  one  ray  direct 

1  Although  the  sextant  is  of  little  use  for  motor  boats 
its  description  and  method  of  adjustment  is  given  here  for 
general  information. 


32    SMALL  BOAT  NAVIGATION 

and  the  other  ray  by  double  reflection.  Its  gen- 
eral form  is  shown  in  Figure  6.  The  frame  is  of 
brass  or  other  composition.  The  graduated  arc 
(cc)  is  generally  of  silver,  the  graduations  being 
by  degrees  and  minutes,  the  smallest  subdivision 
representing  generally  10'.  By  means  of  the  ver- 
nier (d)  the  instrument  can  be  read  to  smaller 
divisions,  usually  10'',  15",  or  20".  The  magni- 
fying glass  (g)  facilitates  reading  the  vernier. 
A  wooden  handle  is  fitted  for  holding  the  instru- 
ment. A  brass  index  arm  (o)  carrying  the  ver- 
nier (d)  is  pivoted  at  the  center  of  the  arc  (cc). 
It  carries  the  index  glass  (a)  which  moves  with 
the  pivot  of  the  index  arm  (o)  as  an  axis.  A 
second  glass  (b),  called  the  horizon  glass,  is  fixed 
to  the  frame.  It  is  half  mirror  and  half  trans- 
parent, the  line  of  demarcation  being  parallel  to 
the  plane  of  the  instrument.  Both  glasses  are 
perpendicular  to  the  plane  of  the  instrument  and 
are  provided  with  adjusting  screws  to  permit  of 
adjustment. 

The  index  arm  can  be  clamped  in  position  on  the 
arc  (cc)  by  the  clamp  (e)  and  the  tangent  screw 
(f)  can  give  the  arm  small  movements  after  it  is 
clamped.  A  telescope  (i),  supported  in  an  ad- 
justable ring  on  the  frame,  is  used  to  give  greater 
distinction  to  the  images.  In  lieu  of  this  tele- 
scope the  star  telescope  (k)  or  plain  sighting  tube 


INSTRUMENTS,  BOOKS,  ETC,    33 

(1)  may  be  used.  Colored  shades  (hh)  are  fitted 
before  the  index  and  horizon  glasses  to  protect  the 
eje  from  sun  glare.  The  same  result  obtains  by 
using  the  colored  cap  (n)  on  the  telestope. 

The  vernier  (d)  is  constructed  on  the  same  prin- 
ciple as  that  explained  under  the  barometer. 

To  Use  the  Sextant  for  measuring  angles  pro-* 
ceed  as  follows :  Point  the  telescope  at  the  lower 
object,  if  one  is  above  the  other,  or  at  the  left 
hand  object,  if  both  are  in  nearly  the  same  hori- 
zontal plane.  Keep  this  object  in  direct  view 
through  the  transparent  part  of  the  horizon  glass, 
and  move  the  index  arm  until  the  reflection  of  the 
second  object  is  seen  in  the  silvered  part  of  the 
horizon  glass.  When  the  objects  are  nearly  in 
coincidence,  clamp  the  index  arm  and  by  the  tan- 
gent screw  bring  the  objects  in  exact  coincidence 
at  the  line  of  demarcation  on  the  horizon  glass. 
The  angle  between  the  objects  is  now  shown  on  the 
arc.  When  measuring  the  height  of  an  object 
above  the  horizon  the  nearest  point  of  the  horizon, 
directly  below  the  object  must  be  employed.  To 
find  this  point  swing  the  instrument  about  the  line 
of  sight  as  a  center,  keeping  the  image  of  the  ob- 
ject in  the  middle  of  the  field.  The  object  will 
appear  to  describe  the  arc  of  a  circle,  the  lowest 
point  of  which  marks  the  vertical.  When  bring- 
ing a  celestial  object  doi^  to  the  horizon  it  is 


34    SMALL  BOAT  NAVIGATION 

usual  to  set  the  instrument  to  zero  and  point  it  at 
the  object.  Then  keeping  the  object  in  the  field 
move  the  index  arm  until  the  horizon  appears  in 
the  field. 

Adjustments  of  Sextant,  The  adjustments 
ordinarily  made  by  the  navigator  are  to  keep  the 
horizon  and  index  glasses  perpendicular  to  the 
plane  of  the  instrument,  and  the  line  of  sight  par- 
allel to  the  plane  of  the  instrument. 

Adjustment  of  the  Index  Mirror.  Clamp  the 
arm  near  the  middle  of  the  arc.  Place  the  eye 
near  the  index  mirror  and  sight  along  the  plane 
of  the  instrument.  If  the  direct  and  reflected  im- 
ages of  the  arc  appear  in  one  plane  the  index  mir- 
ror is  in  adjustment,  perpendicular  to  the  plane 
of  the  instrument.  If  the  reflected  image  of  the 
arc  appears  to  droop  from  the  direct  image  the 
glass  leans  backward;  if  it  seems  to  rise  the  glass 
leans  forward.  Adjust  by  screws  back  of  the 
mirror. 

Adjustment  of  the  Horizon  Mirror,  Having 
adjusted  the  index  mirror,  select  a  celestial  ob- 
ject, preferably  a  star,  to  adjust  the  horizon  mir- 
ror. Put  in  the  telescope  and  direct  it  toward  a 
star.  Move  the  index  arm  until  the  reflected  im- 
age passes  the  direct  image.  If  one  passes  di- 
rectly over  the  other  the  mirror  is  in  adjustment. 
If  one  passes  to  one  side  of  the  other,  adjust  the 


INSTRUMENTS,  BOOKS,  ETC.    35 

horizon  mirror  by  its  attached  screws  until  the 
images  pass  one  over  the  other. 

Adjustment  of  the  Line  of  Sight  is  more  diffi- 
cult. Screw  the  star  telescope,  which  has  two 
parallel  wires  in  its  eye  piece,  into  the  ring;  turn 
the  eye  piece  until  the  wires  are  parallel  to  the 
plane  of  the  instrument.  Select  two  well  defined 
objects  whose  angle  is  greater  than  90°  (stars 
preferred).  Bring  these  objects  into  coincidence 
at  one  wire  of  the  eye  piece.  Now  move  the  in- 
strument until  they  are  seen  at  the  other  wire.  If 
still  in  coincidence  the  line  of  sight  is  in  adjust- 
ment. If  not,  correct  by  the  adjusting  screws  of 
the  ring. 

The  Index  Error  of  a  sextant  is  an  error  in  its 
reading  due  to  the  fact  that  when  both  mirrors 
are  parallel  the  zero  of  the  vernier  does  not  co- 
incide with  the  zero  of  the  arc.  This  error  does 
not  necessarily  remain  constant  and  it  is  good 
practice  to  determine  it  each  time  the  instrument 
is  used. 

The  Index  Correction,  which  is  the  index  error 
with  its  algebraic  sign  reversed,  is  the  correction 
that  must  be  applied  to  an  observed  angle  to  get 
the  true  angle.  It  may  be  found  by  observation 
on  (a)  a  star,  (b)  the  sea  horizon,  (c)  the  sun. 

(a)  Bring  the  direct  and  reflected  images  of 
the  star  into  coincidence  and  read  the  sextant. 


36    SMALL  BOAT  NAVIGATION 

This  reading  is  the  index  correction,  and  is  +  ^^ 

—  according  as  the  vernier  zero  is  to  the  right  or 
left  of  the  zero  on  the  arc. 

(b)  Proceed  in  a  similar  manner,  substituting 
the  sea  horizon  for  the  star. 

(c)  Bring  the  upper  limb  of  the  direct  image 
of  the  sun  tangent  to  the  reflected  lower  limb. 
Read  the  instrument  and  mark  the  reading  +  or 

—  as  in  (a).  Now  bring  the  lower  limb  of  the 
direct  image  tangent  to  the  reflected  upper  limb. 
Read  the  instrument  and  give  the  proper  alge- 
braic sign  according  to  the  above  rule.  One  half 
the  algebraic  sum  of  the  two  readmgs  is  the  index 
correction. 

Of  these  three  methods  the  first  is  preferable  as 
it  is  the  most  accurate.  Always  make  contact  by 
moving  the  tangent  screw  in  the  same  direction. 

The  Koch  Protractor  is  one  of  the  most  use- 
ful instruments  known  to  piloting.  It  combines 
all  the  facilities  of  a  portable  compass  rose,  the 
parallel  rulers,  the  protractor,  and  the  plotter. 
It  is  described  at  length  in  the  next  chapter. 

g.    BOOKS  AND  ACCESSORIES 

(a)  Charts.  A  full  set  of  coast  and  harbop 
charts  should  be  on  hand  for  all  waters  that  it  is 
intended  to  visit,  or  that  any  emergency  might 
cause  the  owner  to  visit.     Before  sailing  care  must 


INSTRUMENTS,  BOOKS,  ETC.    37 

be  taken  to  see  that  these  charts  are  corrected  to 
date.  A  weekly  bulletin  issued  by  the  U.  S.  Hy- 
drographic  Office,  Washington,  D.  C,  supplies  all 
corrections  and  can  be  had  on  request.  An  un- 
corrected chart  is  not  infrequently  the  cause  of 
grounding.  Large  scale  harbor  charts  should  be 
obtained  for  all  harbors  and  inland  waters  that 
may  be  visited. 

The  following  various  publications,  issued  by 
the  Hydrographic  Office,  dealing  with  special  fea- 
tures of  navigation,  should  be  regularly  consulted. 
They  can  be  found  at  any  branch  Hydrographic 
Office  in  the  large  sea  ports. 

Pilot  Charts  of  the  various  oceans,  which  fur- 
nish information  about  drifting  derelicts,  ice  and 
floating  obstructions,  storm  tracks,  average  wind 
and  weather,  ocean  currents,  etc. 

Hydrographic  Btdletin,  weekly,  which  gives 
weekly  changes  of  the  above. 

DaUy  Memorandum,  which  gives  daily  informa- 
tion of  interest  to  mariners. 

Notices  to  Mariners,  which  are  weekly  bulletins 
of  changes  in  aids  to  navigation  (lights,  buoys, 
etc),  dangers  to  navigation  (rocks,  shoals,  bars, 
etc.),  and  in  general  all  facts  that  affect  charts, 
sailing  directions,  etc.  All  charts  and  sailing  di- 
rections should  be  kept  corrected  to  date  from 
these  notices. 


38    SMALL  BOAT  NAVIGATION 

(b)  A  Light  and  Buoy  List  of  latest  date 
must  be  carried.  It  consists  of  a  list  of  lights  and 
buoys  with  their  location  (Latitude  and  Longi- 
tude), their  descriptions  and  characteristics,  and 
other  information  such  as  fog  signal  stations  and 
submarine  signal  stations.  It  can  be  obtained 
from  the  Hydrographic  Office  and  must  be  kept 
corrected  to  date  in  a  similar  manner  to,  and  from 
the  same  source  as,  the  charts. 

(c)  Sailing  Dikections  of  that  part  of  the 
world  to  be  navigated  should  be  carried.  They 
come  in  bound  volumes,  each  volume  covering  a 
large  tract  of  pilot  waters.  They  give  detailed 
information  of  harbors,  coasts,  currents,  courses 
for  entering  harbors,  cable,  provision  and  coaling 
facilities,  in  fact  are  indispensable  fonts  of  navi- 
gational data.  They  are  obtained  from  the  same 
source  as  the  charts  and  are  corrected  from  the 
same  publications.  For  American  waters  use 
U.  S.  Coast  Pilots. 

(d)  Bowditch's  Useful  Tables  (latest 
date)  should  be  used.  This  book  contains  48  dif- 
ferent tables,  and  these  comprise  all  the  tables 
needed  for  any  coasting  or  piloting  problem  that 
may  arise. 

(e)  Tide  Tables  and  the  Nautical  Ephemeris 
of  the  current  year  may  be  carried  but  are  not 
necessary  while  on  pilot  waters.     The  Nautical 


INSTRUMENTS,  BOOKS,  ETC.    39 

Ephemeris  will  be  needed  if  any  celestial  observa- 
tions are  made,  and  in  this  case  a  well  rated  chro- 
nometer will  also  be  necessary.  The  time  of  high 
and  low  water  for  any  port  may  be  obtained  from 
the  local  paper. 

~      3.    RECORDS  THAT  SHOULD  BE  KEPT 

(a)  The  Log  Book  is  a  record  of  the  vessel's 
cruise,  and  is  a  most  necessary  accessory.  It 
should  contain  aU  the  data  of  the  navigation  by 
dead  reckoning,  and  should  afford  a  complete  me- 
teorological record.  In  addition  all  occurrences  of 
note  should  be  recorded.  It  is  the  only  available 
legal  record  in  case  of  crime  or  accident  on  board. 

Hourly  data.  The  following  hourly  data 
should  be  entered  in  the  log  at  the  end  of  each 
hour. 

1.  Knots,  to  nearest  tenths,  made  good  during  the  hour. 

2.  Patent  log  reading,  if  one  is  carried. 

3.  The  average  engine  revolutions  for  the  hour. 

4.  Courses  steered  during  the  hour.  (The  exact  time  of 
changing  course,  with  the  patent  log  reading  at  that  time 
should  be  recorded.  This  data  is  used  to  work  up  the  dead 
reckoning,  which   is  discussed  later.) 

6.  The  wind,  its  force  and  direction. 

6.  The  barometer,  and  its  attached  thermometer. 

7.  The  thermometer,  both  wet  and  dry  bulb. 

8.  The  temperature  of  the  sea  water. 

9.  State  of  weather. 

10.  Clouds,  form,  quantity,  and  direction  from  which 
moving. 

11.  State  of  sea. 


40    SMALL  BOAT  NAVIGATION 

The  information  in  1,  2,  3,  and  4  is  used  for 
navigation. 

The  information  in  5,  6,  7,  9,  10,  and  11  is  used 
to  foretell  the  weather.  (8)  The  temperature  of 
the  sea  water  will  help  detect  the  proximity  of  ice, 
or  the  presence  of  a  cold  or  hot  current,  such  as 
the  Gulf  Stream. 

The  Force  of  the  Wmd  (5)  is  recorded  numer- 
ically from  0  (a  calm)  to  12  (a  hurricane).  Ad- 
miral Beaufort  devised  a  convenient  scale  which  is 
given  in  part  below: 


Force   of   Wind. 

Velocity  in  Statute 
Miles  'per  Hour. 

0  — Calm 

0-3 

1  —  Light  air 

8 

2  — Light  breeze 

13 

3  —  Gentle  breeze 

18 

4  —  Moderate  breeze 

23 

5  —  Fresh  breeze 

28 

6  —  Strong  breeze 

34 

7  —  Moderate  gale 

40 

8  — Fresh  gale 

48 

9  —  Strong  gale 

56 

10  — Whole  gale 

65 

11  —  Storm 

75 

12  —  Hurricane 

90  and  over. 

The  State  of  the  Weather  (9)  is  entered  in  the 
log  by  symbols  as  follows : 


INSTRUMENTS,  BOOKS,  ETC.     41 

b  —  Clear  blue  sky.  p  —  Passing  rain  showers, 

c  —  Clouds  present  in  sky.       q  —  Squally  weather. 
d  —  Drizzling.  r  —  Continuous  rain, 

f  —  Foggy.  s  — Snow  falling. 

g  —  Gloomy,    stormy  look-      t  —  Thunder.. 

ing.  u  —  Ugly     or     threatening 

fa  —  Hail.  ,  weather. 

1  —  Lightning.  v  —  Variable  weather, 

m  —  Misty.  w  —  Heavy  dew. 

o  —  Overcast  sky.  z  —  Hazy  weather. 

Clouds.  In  the  scale  for  the  amount  of  clouds, 
0  represents  a  clear  cloudless  sky  and  10  a  sky 
entirely  overcast.  The  amount  of  clouds  is  re- 
corded in  tenths  of  the  sky  covered  by  them.  The 
following  are  the  principal  forms  of  clouds,  given 
in  order  of  their  altitude  above  the  earth,  begin- 
ning with  the  most  elevated. 

1.  Cirrus  (Ci.) — Detached  delicate,  fibrous  looking 
clouds,  in  the  form  of  feathers,  generally  white,  sometimes 
arranged  in  belts  converging  toward  one  or  two  points  of 
the  horizon. 

2.  Cirro-stratus  (Ci.-S.)  —  A  thin  whitish  sheet  or  a 
tangled  web  formation.  The  sheet  formation  sometimes 
causes  halos  around  the  sun  or  moon. 

3.  Cirro-Cumulus  (Ci.-Cu.)  —  Small  globular  masses  or 
white  flakes,  having  no  shadows,  or  very  light  ones,  arranged 
in  groups  or  lines. 

4.  Alto-Cumulus  (A.-Cu.) — Large  globular  whitish  or 
grayish  masses,  partially  shaded,  arranged  in  groups  or 
belts. 

6.  Alto-Stratus  (A.-S.)  — A  thick  sheet  of  grayish  or 
bluish  color,  showing  a  brilliant  patch  in  the  neighborhood 
of  the  sun  or  moon,  but  does  not  produce  halos.  This  form 
of  cloud  is  similar  to  the  Cirro-Stratus  but  is  only  about 
half  as  high. 


42    SMALL  BOAT  NAVIGATION 

6.  Strato-Ctimulus  (S.-Cu.) — Large  globular  masses  or 
rolls  of  dark  cloud,  frequently  covering  the  whole  sky, 
especially  in  winter.  It  differs  in  appearance  from  the  nim- 
bus in  this  globular  or  rolled  appearance,  and  does  not  bring 
rain. 

7.  Nimhvs  (N.)  —  Rain  clouds;  a  thick  layer  of  dark 
clouds  without  shape  and  having  ragged  edges.  Through 
the  opening  in  these  clouds  an  upper  layer  of  Cirro-Stratus 
or  Alto-Stratus  may  almost  invariably  be  seen.  Loose 
clouds  visible  floating  at  a  low  level  under  a  Nimbus  sheet 
are  Fracto-Nimbus  (Fr.-N.),  called  by  sailors  "scud" 

8.  Cumulus  (Cu.) — Wool-pack  clouds;  thick  clouds  of 
which  the  upper  surface  is  dome-shaped  and  exhibits  pro- 
tuberances, while  the  base  is  horizontal.  The  true  Cumu- 
lus has  clear  superior  and  inferior  limits.  It  is  often 
broken  up  by  strong  winds,  and  the  detached  portion  is 
called  Fracto-Cumulus  (Fr.-Cu). 

9.  Cumulo-Nimbus  (Cu.-N.) — The  thunder-cloud  or 
shower-cloud;  heavy  masses  of  clouds  in  the  form  of  tur- 
rets, mountains,  or  anvils,  generally  having  a  fibrous  sheet 
above,  and  Nimbus  beneath.  From  the  base  are  generally 
seen  showers  descending. 

10.  Stratus  (S.) — A  horizontal  sheet  of  lifted  fog; 
when  broken  up  by  wind  it  is  called  Fracto-Stratu* 
(Fr.-S.). 

The  State  of  the  Sea  is  recorded  by  the  follow- 
ing symbols: 

B  —  Broken  or  irregular  sea.  M  —  Moderate  sea  or  swell. 

C  —  Chopping,  short  or  cross  R  —  Rough  sea, 

G  —  Ground  swell.  S  —  Smooth  sea. 

H  —  Heavy  sea.  T  —  Tide  rips. 
L  —  Long  rolling  sea. 

(b)  The  Navigator's  Note  Book.  The 
navigator  should  keep  a  note  book  in  which  to 
enter  all  the  bearings  and  observations  taken,  and 


INSTRUMENTS,  BOOKS,  ETC.     43 

all  work  and  calculations  connected  therewith.  It 
should  form  a  complete  history  of  all  navigation 
performed, 

4.     REPORTS    MADE 

Anything  of  an  unusual  nature  should  be  re- 
ported to  the  Hydrographic  Office  at  Washing- 
ton; derelicts  sighted,  icebergs,  any  buoy  or 
marker  that  is  suspected  to  be  out  of  position,  any 
light  that  is  out  or  that  is  not  showing  in  accord- 
ance with  its  latest  description  in  the  Light  List, 
any  unusual  meteorological  phenomenon,  in  fact 
anything  that  will  promote  safe  navigation,  should 
be  reported.  Every  mariner  should  have  the  best 
interests  of  the  brotherhood  at  heart. 

All  navigational  information  in  this  country 
emanates  from  the  Hydrographic  Office  and  it  is 
entitled  to  the  aid  of  every  person  who  performs 
navigation. 


CHAPTER  ni 

THE    vessel's    position 

THE  bearing  of  an  object  from  a  ves- 
sel is  the  direction  in  which  the  object 
is  seen  from  the  vessel.  It  is  the  angle  be- 
tween the  meridian  passing  through  the  observer 
and  the  object.  It  is  called  true,  magnetic,  or 
compass,  depending  upon  the  meridian  of  refer- 
ence chosen.     This  is  explained  later. 

A  Line  of  Position  is  any  line  on  which  the 
vessel's  position  is  known  to  be,  that  can  be  plotted 
on  a  chart. 

A  Line  of  Bearing  is  any  line  of  position  ob- 
tained from  a  bearing. 

A  Position  Point  is  any  point  on  either  a  line 
of  position  or  a  line  of  bearing  at  which  the  ves- 
sel's position  is  known  to  be.  A  position  point, 
generally  called  a  "  ^,"  can  be  obtained  by  the 
intersection  of  two  lines  of  position,  two  lines  of 
bearings,  or  one  of  each. 

COMPASS  ERROR 

Variation  of  the  Compass.  Since  the  earth's 
magnetic  pole  in  each  hemisphere  differs  in  geo- 


THE  VESSEL'S  POSITION     45 

graphical  position  from  the  geographical  pK)le, 
the  earth's  magnetism  will  cause  the  compass  nee- 
dle to  point  to  a  spot  (the  magnetic  pole)  that  is 
different  from  the  geographical  pole'  (called  the 
true  pole).  Hence  the  compass  needle  will  point 
at  an  angle  to  the  true  meridian.  The  geograph- 
ical pole  lies  true  North  of  all  points  in  the  North- 
ern hemisphere.  The  angle  that  the  great  circle 
through  the  observer's  position  and  the  magnetic 
pole  makes  with  the  true  meridian  (viz:  the  great 
circle  through  the  geographical  pole)  is  called  the 
variation. 

This  variation  differs  for  different  points  on  the 
earth.  The  variation  for  any  given  locality  is 
shown  on  the  charts.  A  nautical  chart  always 
contains  the  data  from  which  the  navigator 
can  find  the  variation  for  any  locality  for  any 
year. 

Deviation  of  the  Compass.  In  addition  to 
the  variation,  the  compass  ordinarily  has  a  still 
further  error  in  its  reading.  This  arises  from 
the  effect  produced  on  it  by  masses  of  magnetic 
metal  in  the  vessel  itself.  Deviation,  which  is 
produced  by  attraction  of  the  compass  needle  by 
magnetic  iron  within  the  vessel  itself,  varies  for 
different  vessels,  different  headings  of  the  same 
vessel,  and  undergoes  change  as  a  vessel  proceeds 
from  one  geographical  locality  to  anothen     A 


46    SMALL  BOAT  NAVIGATION 

table  compiled  to  show  the  deviation  on  all  head- 
ings is  called  a  deviation  table. 

The  Compass  Error  is  the  algebraic  sum  of 
the  variation  and  deviation.  As  stated  before  the 
variation  can  be  obtained  from  a  chart.  The  de- 
viation is  obtained  from  a  deviation  table  which  is 
constructed  by  "  swinging  ship."  This  and  the 
operation  of  "  compensating  the  compass "  are 
beyond  the  scope  of  the  average  amateur,  but  in 
all  ports  are  mariners  who  make  a  specialty  of  this 
work.  The  simplest  method  of  "  swinging  ship  " 
for  deviation,  that  by  ranges,  is  described  on  page 
49. 

From  what  has  gone  before  it  is  seen  that  there 
are  three  methods  by  which  bearings  and  courses 
may  be  expressed:  (1)  true,  when  referred  to  the 
geographical,  or  true,  meridian;  (2)  magnetic, 
when  referred  to  the  magnetic  meridian;  and  (3), 
compass,  when  referred  to  the  meridian  in  which 
the  compass  needle  lies. 

To  convert  compass  bearings  or  courses  to  mag- 
netic bearings  or  courses  it  is  necessary  to  apply 
the  deviation,  corresponding  to  the  vessel's  head- 
ing, to  the  compass  bearings  or  courses.  Likewise 
to  convert  magnetic  hearings  to  true  hearings  the 
variation  for  the  locality  must  be  applied  to  the 
magnetic  bearings. 

The  process  of  applying  variation,  deviation, 


THE  VESSEL'S  POSITION      47 


and  compass  error  under  all  circumstances  is  one 
with  which  the  navigator  must  become  thoroughly 
familiar;  these  various  problems  are  constantly 
arising;  no  bearing  can  be  plotted,  orr  course  ac- 
curately set,  without  involving  this  problem,  and 
careful  study  of  this  subject  is  recommended. 

When  the  effect  of  a  compass  error,  whether 
arising  from  variation  or  deviation,  is  to  draw  the 
North  end  of  the  compass  needle  to  the  right  the 


Fio.  7. —  Compass  Error.    Fio.  8. 

error  is  named  East  or  is  marked  +  ?  when  its  ef- 
fect is  to  draw  the  North  end  of  the  needle  to  the 
left  it  is  named  West,  or  marked  — . 

Figures  7  and  8  represent,  respectively,  exam- 
ples of  Easterly  and  Westerly  errors.  In  both 
figures  consider  that  the  circles  represent  the  ob- 
server's horizon,  N.  and  S.  being  the  true  North 
and  South  points  in  each  case.  If  N.'  and  S.'  rep- 
resent the  corresponding  points  indicated  by  a 


48    SMALL  BOAT  NAVIGATION 

compass  whose  needle  is  deflected  by  a  compass 
error,  then  in  Fig.  7,  the  North  end  of  the  nee- 
dle being  drawn  to  the  right  the  error  is  Easterly 
or  plus,  and  in  Fig.  8,  the  North  end  of  the  needle 
being  drawn  to  the  left  the  error  is  Westerly  or 
minus. 

Considering  Fig.  7,  if  we  assume  the  Easterly 
error  to  be  one  point,  it  is  apparent  that,  if  a  di- 
rection N.  by  W.  is  indicated  by  the  compass,  the 
true  direction  is  N.,  or  one  point  to  the  right. 
Similarly,  if  the  compass  direction  is  N.  by  E.,  the 
true  direction  is  N.N.E.,  or  still  one  point  to  the 
right.  If  we  follow  around  the  whole  compass 
card,  the  same  relation  will  still  hold  in  every  case, 
the  true  direction  being  always  one  point  to  the 
right  of  the  compass  direction.  Thus,  if  the  com- 
pass direction  is  South,  the  true  direction  is  S. 
by  W.  To  understand  this  consider  that  you 
stand  in  the  center  of  the  compass  card  facing  in 
the  direction  of  the  compass  reading. 

In  Fig.  8,  assuming  the  compass  error  to  be  one 
point  Westerly,  the  converse  of  the  above  holds 
true.  All  true  directions  are  one  point  to  the  left 
of  the  corresponding  compass  directions.  Thus, 
if  the  compass  direction  is  N.  by  E.,  the  true  di- 
rection will  be  North. 

A  few  simple  rules  should  be  remembered  when 
working  compass  problems: 


THE  VESSEL'S  POSITION      49 

1.  When  the  true  bearing  is  to  the  right  of  the 
compass  bearing  the  error  is  East, 

2.  When  the  true  bearing  is  to  the  left  the  error 
is  West, 

8.  When  applying  the  compass  error  imagine 
yourself  standing  in  the  center  of  the  compass 
card,  facing  the  direction  involved  in  the  problem. 

4.  Deviation  plus  variation  equals  compass 
error.  This  means  the  algebraic  sum:  thus,  if 
variation  is  5°  E.  (  +  ),  and  deviation  is  3°  W. 
( — ),  compass  error  is  2°  E.  (  +  ). 

5.  To  convert  from  compass  to  magnetic  direc- 
tion, if  the  magnetic  direction  is  to  the  right,  the 
deviation  is  Easterly.  Conversely,  to  convert  a 
compass  direction  to  a  magnetic  direction,  if  the 
deviation  is  Easterly,  apply  it  to  the  right  of  the 
compass  bearing,  if  Westerly  to  the  left. 

6.  To  convert  from  magnetic  to  true  directions, 
apply  the  variation  to  the  right  of  the  magnetic 
direction  if  the  variation  is  Easterly,  and  to  the 
left  if  Westerly. 

Swinging  Ship  foe  Deviation.  Variation  for 
any  locality  can  be  obtained  from  the  chart  of  that 
locality.  To  find  the  compass  error  on  any  ves- 
sel heading  it  is  necessary  to  know  the  deviation  on 
that  heading.  The  simplest  way  of  determining 
the  deviation  on  the  various  compass  headings  of  a 
Tessel  is  to  swing  ship  by  the  method  of  ranges. 


50    SMALL  BOAT  NAVIGATION 

A  Range  consists  of  two  well  defined  and 
charted  objects  in  line  with  each  other.  The  di- 
rection of  the  line  through  these  two  objects  can 
be  ascertained  from  the  chart.  Ranges  whose 
magnetic  bearings  are  known  have  been  formed 
naturally  or  have  been  laid  out  for  the  aid  of  navi- 
gation in  nearly  all  localities. 

To  obtain  the  deviation  on  various  compass 
headings  of  a  vessel  (a  deviation  table)  proceed 
as  follows:  Having  located  a  magnetic  range, 
steam  across  this  range  on  various  compass  head- 
ings (every  compass  point  if  time  and  circum- 
stances permit).  Steady  on  the  course  for 
three  minutes  before  crossing  the  range.  Observe 
the  compass  bearings  (on  each  heading)  of  the 
range  when  the  two  objects  are  in  line  as  observed 
from  the  vessel.  The  deviation  for  each  heading 
is  the  difference  between  the  compass  bearing  of 
the  range  on  that  heading  and  the  known  magnetic 
bearing  of  the  range.  Rule. —  The  deviation  is 
Easterly  when  the  magnetic  hearing  is  to  the  right 
of  the  compass  bearing,  and  Westerly  when  the 
magnetic  bearing  is  to  the  left  of  the  compass 
hearing. 

An  example  will  serve  to  clear  up  the  above: 
Suppose  the  magnetic  bearing  of  the  range 
is  N.E.  (N.45°E.).  Steaming  across  the  range 
the  compass  bearing  on  each  point  of  compass 


THE  VESSEL'S  POSITION     51 

heading  ^    is    taken    as    follows    (columns    1    and 
8): 


Column  1 

Compass 

Heading 

Column  2 
Compass 
Bearing  of 
Range 

Bearing  of 

Range 

Column  3 

Magnetic 

Column  4 
Deviation 

N 

N  \r  E 

N  45°  E 

2  W 

N   by   E 

N  48**  E 

>» 

3  W 

NNE 

N  49°  E 

» 

4  W 

NE  by  N 

N  ^r  E 

>» 

9  W 

NE 

N  45''  E 

>j 

0 

NE  by  E 

N  43°  E 

>» 

2  E 

EXE 

N  42°  E 

» 

3  E 

E  by  N 

N  41°  E 

n 

4  E 

Record  in  column  3  the  magnetic  bearing  of  the 
range.  To  obtain  column  4«  take  the  numerical 
differences  between  columns  2  and  3  and  mark  the 
results  East  or  West  according  to  the  rule  given 
above. 

Before  Stomgmg  Ship  see  that  all  portable  metal 
objects,  especially  those  near  the  compass,  are 
secured  in  the  positions  habitually  occupied  by 
them  at  sea.  A  change  in  the  position  of  metal 
objects  near  the  compass  will  affect  its  deviation. 
See  that  the  vessel  is  on  an  even  keel.  This  rule 
also  applies  when  taking  bearings.  Steam  across 
the  course  slowly,  having  enough  headway  to  keep 
a  steady  course. 
»  Only  eight  compass  points  arc  taken  for  demonstration. 


52    SMALL  BOAT  NAVIGATION 

The  navigator  should  swing  ship  when  practical 
before  any  long  trip,  or  after  laying  in  port  any 
very  long  interval.  It  is  not  necessary  to  obtain 
the  deviation  on  every  compass  point.  If  a  table 
of  deviations  on  every  other  point  is  constructed 
the  deviation  on  intermediate  points  can  be  inter- 
polated. 

THE  VESSEL'S  POSITION 

Finding  the  Vessel's  Position,  when  piloting, 
resolves  itself  into  four  general  cases: 

1.  To  get  the  vessel's  position  when  one  object 
of  known  position  is  in  sight. 

%  To  get  the  vessel's  position  when  two  objects 
of  known  position  are  in  sight. 

3.  To  get  the  vessel's  position  when  more  than 
two  objects  of  known  position  are  in  sight. 

4.  To  get  the  vessel's  position  when  no  objects 
of  known  position  are  in  sight. 

Case  4  is  a  method  of  soundings  and  as  such  is 
discussed  in  Chapter  5  under  that  heading. 

(1)  To  Get  the  Vessel's  Position  When 
One  Object  of  Known  Position  Is  in  Sight. 

(a)  By  hearing  and  distance.  Take  a  com- 
pass bearing  of  the  object.  Convert  this  bearing 
to  magnetic  or  true  bearing  by  applying  deviation 
or  compass  error.  Plot  this  line  of  bearing  on  the 
chart  by  means  of  parallel  rulers,  using  the  mag- 


THE  VESSEL'S  POSITION      53 

netic  or  true  compass  rose,  depending  upon 
whether  the  bearing  has  been  converted  to  a  mag- 
netic or  true  bearing.  The  vessel  lies  somewhere 
on  this  line.  If  the  distance  from  the  object  can 
be  obtained,  an  arc  of  this  length  with  the  object 
as  a  center  will  intersect  the  line  of  bearing  at  the 
vessel's  position. 

The  distance  may  be  estimated,  but  this  is  of 
doubtful  value.  An  estimated  distance  may  be 
verified  by  a  sounding,  if  the  bottom  is  very  irregu- 
lar so  that  a  characteristic  sounding  may  be  ob- 
tained. 

The  distance  from  an  object  may  be  found  by 
the  vertical  angle  method  if  the  height  of  the  ob- 
ject is  known,  and  the  angle  the  object  subtelids 
at  the  observer  can  be  measured.  The  heights  of 
all  lighthouses  are  given  in  the  Light  List.  Meas- 
ure the  angle  subtended  by  the  lighthouse  by 
means  of  a  sextant.  Now 
h 

d=:.567  — 
O 

where    4  =  <iistance  required  in  knots 
h  =  height  of  lighthouse 
0  =  angle  measured,  in  minutes  of  arc. 

Example;  —  A  lighthouse  150  feet  high  subtends  an  angle 
of  1^;  find  the  distance. 

150 

d  = X  .567  =  7.09  miles  (nautical) 

19 


54    SMALL  BOAT  NAVIGATION 

Table  3S  of  Bowditch's  Tables  (Edition  of 
1913)  can  be  used  to  solve  problems  of  the  above 
kind.  Enter  the  column  corresponding  to  the 
height  of  the  object.  Find  the  angle  nearest  to 
that  measured,  and  on  the  same  line  (in  the  first 
column)  is  found  the  distance  of  the  object. 

(b)  By  Two  Bearings  of  a  Single  Object  and 
the  Course  and  Distance  Run  in  the  Interval,     In 


Fig.  9. —  Position  by  two  bearings  and  interval  run. 

Figure  9,  assume  A  is  the  object  on  which  bearings 
are  taken.  The  vessel  being  at  B,  the  bearing 
BA  is  taken  and  the  patent  log  is  read.  The  ves- 
sel then  steers  a  course  BC  and  at  C  the  bearing 
CA  is  taken  and  the  patent  log  is  read.  The  dif- 
ference of  patent  log  readings  is  the  distance  BC. 
(Note:  If  no  patent  log  is  carried  the  distance 
BC  can  be  computed  by  knowing  the  speed  at 


THE  VESSEL'S  POSITION      55 

which  the  vessel  is  sailing  and  the  time  it  takes  to 
run  the  distance  BC.)  From  the  course  steered 
and  the  bearings  BA  and  CA  the  angles  B  and  C 
can  be  computed  and  BAG  =  180-— (B  +  C). 
The  problem  is  one  of  plane  trigonometry,  given 
two  angles  and  one  side  of  a  plane  triangle.  It 
can  be  solved  in  three  ways : 

(A)  by  plane  trigonometry, 

(B)  by  Bowditch's  Tables, 

(C)  by  graphic  chart  work, 

(A)  This  method  is  little  used,  the  last  two 
being  far  simpler.     By  plane  trigonometry, 

sin  C 
AB  = X  BC 

sin  A 

sin  B 
AC= XBC 

sin  A 

Dropping  the  perpendicular  AD  from  A  to  BC, 
the  distance  of  the  object  when  abeam  is 

AD  =  AC  sin  C. 

(B)  Tables  6 A  and  5B,  Bowditch,  are  com- 
piled for  an  inspection  solution  of  this  problem. 
The  arguments  in  these  tables  are  the  difference 
between  the  course  and  the  first  bearing,  and  the 
difference  between  the  course  and  the  second  bear- 
ing.    The  differences  in  Table  6A  are  in  quarter 


56    SMALL  BOAT  NAVIGATION 

points,  and  in  Table  5B  are  in  degrees.  The  fac- 
tors in  the  columns  are  for  a  distance  run  of  one 
mile.  So  far  as  the  factors  are  concerned  it  is 
immaterial  whether  the  courses  and  bearings  are 
compass,  magnetic,  or  true,  so  long  as  they  all 
refer  to  the  same  meridian. 

To  use  the  tables:  Enter  the  column  corre- 
sponding to  the  difference  between  the  course  and 
the  first  bearing.  Run  down  this  column  until  the 
line  is  reached  corresponding  to  the  difference  be- 
tween the  course  and  the  second  bearing.  On  this 
line  are  found  two  factors.  Multiply  the  run  be- 
tween bearings  by  the  first  factor  and  the  result 
is  the  distance  of  the  object  at  the  time  of  the  sec- 
ond bearing.  Multiply  the  run  by  the  factor  in 
the  second  column  and  the  result  is  the  distance 
when  the  object  is  abeam. 

Example:  A  vessel  heading  250°  (p.s.c,  per  standard 
compass),  had  a  lighthouse  bearing  202°  (p.s.c.) ;  after  a 
run  of  10  miles  the  same  light  bore  130°  (p.s.c).  Find 
the  distance  at  the  time  of  second  bearing,  also  when 
abeam. 

Difference  between  course  and  first  bearing   48°. 

Difference  between  course  and  second  bearing   ..120°. 

Table  5B,  factor  first  column  =  0.78  and  distance  at  sec- 
ond bearing  =  10  X  0.78  =  7.8  miles. 

Table  5B,  factor  second  column  =  0.68  and  distance  when 
object  is  abeam  =  10  X  0.68  =  6.8  miles. 

(C)  There  is  a  graphic  method  of  solving  this 
problem  that  is  preferred  by  some  navigators  to 


THE  VESSEL'S  POSITION     S7 

the  factor  method  Draw  upon  the  chart  the  lines 
CA  and  BA,  Figure  10,  passing  through  the  ob- 
ject and  having  the  direction  of  the  two  observed 
bearings ;  set  the  dividers  to  the  distance  run,  BC ; 
lay  down  the  parallel  rulers  in  a  direction  parallel 
to  the  course  steered  and  move  them  toward  or 
away  from  the  observed  object  until  such  a  point 


Fm.  10. —  Graphic  method,  two  bearings  and  run. 

is  found  that  the  distance  between  the  lines  of 
bearings  is  equal  to  the  distance  between  the 
points  of  the  dividers.  In  the  figure  this  occurs 
when  the  rulers  lie  along  the  line  BC,  and  there- 
fore B  represents  the  vessel's  position  at  the  time 
of  first  bearing,  and  C  its  position  at  the  time  of 
second  bearing.  For  any  other  positions  B''C", 
B'C,  the  condition  is  not  fulfilled. 


58    SMALL  BOAT  NAVIGATION 

(D)  Special  Problems,  There  are  many  spe- 
cial applications  of  the  above  method  of  obtaining 
the  vessel's  position,  that  are  so  simple  as  to  be- 
come mere  mental  problems.  Some  of  these  are 
given  here : 

Bow  and  Beam  Bearings.  If  the  first  bearing  is 
is  taken  broad  off  the  bow  (45°  from  ahead)  and 


Fig.  11. —  Doubling  Angle  on  the  Bow. 

Note:  In  Figure  11,  suppose  the  angle  observed  be- 
tween the  course  and  the  bearing  at  B  is  9,  and  at  C  is  29. 
Then  the  angle  BAG  equals  9  and  AC  equals  BC. 

the  second  bearing  is  taken  on  the  beam  (90°  from 
ahead),  then  it  is  apparent  from  inspection  that 
the  distance  at  the  time  of  the  second  bearing 
equals  the  distance  run.  Likewise,  if  the  first 
bearing  is  taken  abeam  (90°  from  ahead)  and  the 
second  is  taken  on  the  quarter  (135°  from  ahead). 


THE  VESSEL'S  POSITION     59 

then  the  distance  when  abeam  is  equal  to  the  dis- 
tance run.  The  distance  from  the  object  when  on 
the  bow  and  quarter  is  1.4  times  the  distance  run. 

Doubling  the  Angle  on  the  Bow,  Take  a  bear- 
ing of  an  object  when  forward  of  the  bow;  read 
the  patent  log.  Take  a  second  bearing  of  the  ob- 
ject when  its  angular  distance  from  ahead  is  twice 
as  great  as  it  was  at  the  time  of  the  first  bearing; 
read  the  patent  log.  The  distance  of  the  object 
from  the  vessel  at  the  time  of  the  second  bearing  is 
equal  to  the  distance  run  between  bearings. 

The  261/2°  Rule.  If  the  first  bearing  is  taken 
when  the  object  is  26%°  from  ahead,  and  the  sec- 
ond bearing  is  taken  when  the  object  is  45°  from 
ahead,  then  the  distance  at  which  the  object  wUl  be 
passed  abeam  is  equal  to  the  run  between  the  two 
bearings. 

The  Seven-tenths  Rule.  If  bearings  are  taken 
of  an  object  when  two  and  four  points  on  the  bow, 
seven-tenths  (0.7)  of  the  run  between  bearings  is 
the  distance  at  which  the  object  will  be  passed 
abeam. 

The  Seven-thirds  Rule.  If  bearings  are  taken 
of  an  object  when  two  points  forward  of  the  beam 
(67%°  from  ahead),  and  when  abeam,  seven- 
thirds  (%)  of  the  run  between  bearings  is  approxi- 
mately the  distance  of  the  object  when  abeam. 

If  bearings  are  taken  of  an  object  at  22%°  and 


6o    SMALL  BOAT  NAVIGATION 

26^°  from  ahead,  then  %  of  the  distance  run  be- 
tween bearings  is  approximately  the  distance  at 
which  the  object  will  be  passed  abeam. 

The  method  of  obtaining  the  position  by  two 
bearings  on  the  same  object  is  very  useful,  for  fre- 
quently it  is  necessary  to  locate  one's  position 
when  only  one  landmark  is  in  sight.  A  good  navi- 
gator never  misses  an  opportunity  to  check  his 
position  by  a  bow  and  beam  bearing  on  every  well 
charted  object  passed. 

It  must  always  be  borne  in  mind  that  the  results 
from  this  method  will  be  incorrect  unless  the 
"  course  and  distance  made  good  over  the 
ground "  are  correctly  estimated.  Bad  steering, 
cross  currents,  or  leeway  of  the  vessel  will  cause 
inaccuracy  in  the  estimated  course,  and  a  current 
with  or  against  the  ship,  or  inaccuracy  in  the  dis- 
tance logged  will  affect  the  estimated  distance. 
A  current  with  the  vessel  will  give  a  position  closer 
to  the  charted  object  than  the  actual  position,  and 
a  current  against  the  vessel  will  give  a  position 
farther  away  than  the  actual  distance.  If  the  lo- 
cal current  is  known,  allowance  can  be  made  for  it 
when  working  this  problem. 

(2)  To  Get  the  Vessel's  PosmoN  When 
Two  Objects  of  Known  Position  Are  in  Sight. 
{Cross  Bearings  of  Two  Charted  Objects.) 

Select  two  well  charted  objects  whose  respective 


THE  VESSEL'S  POSITION     6i 

bearings  differ  as  nearly  as  possible  by  90°. 
Take  the  compass  bearings  of  these  objects  when 
the  vessel  is  on  an  even  keel,  and  as  quickly  as  pos- 
sible one  after  the  other.  Correct  the  compass 
bearings  so  that  they  will  be  either  true  or  mag- 
netic, according  to  the  compass  rose  to  be  used 
in  plotting  them,  applying  compass  error  to  ob- 


Fio.  12. —  Position  by  cross  bearings. 

tain  true  bearings,  and  deviation  only  to  obtain 
magnetic  bearings. 

By  means  of  parallel  rulers  draw  through  the 
objects  lines  in  the  respective  directions  that  each 
was  observed  to  bear.  As  the  vessel's  position  is 
known  to  be  on  each  of  these,  it  follows  that  it 
must  be  at  the  intersection.  In  Figure  12,  if  A 
and  B  are  the  objects  and  OA  and  OB  are  the  lines 
passing  through  them  in  the  observed  directions, 


62    SMALL  BOAT  NAVIGATION 

then  the  vessel's  position  is  at  O,  their  intersec- 
tion. The  solution  of  this  problem  is  greatly  fa- 
cilitated by  the  use  of  Koch's  Plotter,  which  is 
described  with  its  uses  at  the  end  of  this  chap- 
ter. 

If  possible,  objects  selected  for  cross  hearings 
should  subtend  an  angle  at  the  vessel  of  at  least  30° 
and  less  than  150°.  As  the  angles  become  smaller 
and  greater  than  these  limits,  small  errors  of  ob- 
servation give  larger  errors  in  the  results.  Near 
objects  are  preferred  to  distant  ones.  When  find- 
ing the  "  fix  "  by  cross  bearings,  take  the  bearing 
of  the  object  nearest  ahead  or  astern  first,  as  that 
object  will  change  its  bearing  less  during  the  in- 
terval between  bearings  than  one  more  nearly 
abeam. 

(3)  To  Get  the  Vessel's  Position  When 
More  than  Two  Objects  Are  in  Sight. 

(a)  Cross  Bearings.  The  method  of  cross 
bearings  on  two  objects  has  been  explained  above. 
If  a  third  well  charted  object  is  in  sight,  its  bear- 
ing should  be  taken  and  plotted  in  the  same  man- 
ner to  be  a  check  on  the  other  two.  If  this  line  of 
bearing  intersects  at  the  same  point,  O  in  Figure 
12,  it  verifies  the  accuracy  of  the  "  fix."  If  not  it 
indicates  an  error,  either  in  the  observations,  plot- 
ting, or  the  application  of  the  compass  error. 
Should  the  three  bearings  form  only  a  very  small 


THE  VESSEL'S  POSITION     63 

triangle  at  their  intersection,  the  center  of  this 
triangle  may  be  taken  as  the  vessel's  position. 

(b)  Three  Point  Problem,^  This  is  the  most 
accurate  method  of  obtaining  a  fix.  Three  ob- 
jects on  the  chart  are  selected  and  the  angles  be- 
tween them  are  measured  by  a  sextant.  In  lieu  of 
a  sextant  the  bearings  of  three  objects  may  be 
taken  and  the  angles  between  them  may  be  com- 
puted therefrom.  The  position  is  plotted  by  a 
Three  Arm  Protractor  (a  description  of  this  in- 
strument is  omitted  because  the  Koch  Plotter  de- 
scribed later  will  perform  all  of  its  functions). 
To  plot,  given  the  angles,  set  the  right  and  left 
angles  on  the  instrument  and  then  move  it  over  the 
chart  until  the  three  bevel  edges  of  the  arms  pass 
respectively  and  simultaneously  through  the  three 
objects.  The  center  of  the  instrument  will  then 
mark  the  fix,  which  may  be  marked  by  a  pencil 
point  through  the  center  hole  of  the  protractor. 

(4)  Danger  Angles.  When  coasting  the 
navigator  will  often  desire  to  pass  sunken  rocks 
or  dangerous  shoals  or  sunken  obstructions  at  a 
minimum  distance.  This  is  done  by  use  of  the 
Danger  Angle,  of  which  there  are  two  kinds,  hori- 
zontal and  vertical.     The  former,  which  is  prefer- 

iThis  method  is  used  extensively  in  marine  surveying. 
It  requires  the  use  of  a  sextant  and  is  of  little  value  to 
motor  boats. 


64    SMALL  BOAT  NAVIGATION 

able,  is  used  when  two  charted  objects  making  a 
fair  angle  are  available,  and  the  latter  when  only 
one  such  object  is  available. 

The  Horizontal  Danger  Angle,^  In  Figure  13, 
suppose  AMB  a  portion  of  the  coast  along  which 
the  vessel  is  coasting,  on  the  course  CD ;  A  and  B 
are  two  well  charted  objects ;  S  and  S'  are  two  out- 
lying shoals  or  reefs  that  must  be  avoided.  To 
pass  outside  the  danger  S'  proceed  as  follows: 
(the  construction  is  shown  in  full  lines)  take  the 
middle  point  of  the  danger  S'  as  a  center,  and  with 
a  radius  equal  to  the  distance  from  the  danger 
that  it  is  desired  to  pass,  describe  a  circle  (the 
small  full  circle).  Now  pass  a  circle  (the  large 
full  circle)  through  A  and  B  tangent  to  the  small 
circle.  Measure  the  angle  AEB,  set  the  sextant 
to  this  angle.  Now  since  AB  subtends  the  same 
angle  at  all  points  of  the  circle  AEB  it  is  appar- 
ent that  as  long  as  AB  does  not  subtend  an  angle 
greater  than  AEB,  the  vessel  will  be  outside  the 
circle  AEB,  hence  clear  of  the  danger  S' 

To  avoid  the  danger  S,  passing  inside  it,  pro- 
ceed in  a  similar  manner  as  follows  (construction 
in  broken  lines)  :  Take  the  middle  point  of  the 
danger  S  as  a  center,  and  with  a  radius  equal  to 

iThis  requires  the  use  of  a  sextant.  The  knowledge  is 
unnecessary  but  is  inserted  for  the  use  of  the  navigator 
who  possesses  a  sextant. 


THE  VESSEL'S  POSITION     65 

the  distance  it  is  desired  to  pass  the  danger,  de- 
scribe a  circle  (the  small  broken  circle).  Through 
A  and  B  draw  a  circle  tangent  to  the  first  circle 


Fm.  is.— Horizontal  Danger  Angle. 


(large  broken  circle).  Measure  the  angle  A6B 
with  a  protractor  and  set  the  sextant  to  this  an- 
gle.    Now    as    long   as    AB    subtends    an   angle 


66    SMALL  BOAT  NAVIGATION 

greater  than  AGB  the  vessel  will  pass  inside  the 
danger  S.  By  combining  the  two  methods,  the 
ship  will  pass  safely  between  the  dangers  as  long 
as  the  angle  subtended  by  AB  is  less  than  AEB 
and  greater  than  AGB. 

Vertical    Danger    Angle,     Figure     14».     This 


y 

\ 

/          ^ 

\ 

*^          \ 

/           y"^ 

\      \ 

1           /               v 

\      \ 

/'^N     (""'A 

\ 

)  ] 

y  J 

/ 

Fig.  14. —  Vertical  Danger  Angle. 

method  is  based  on  similar  principles  to  the  hori- 
zontal danger  angle,  the  construction  being  a  lit- 
tle different.  An  object  of  known  height  and  dis- 
tance, such  as  a  lighthouse,  is  used.  Lighthouses 
are  measured  from  mean  high  water  to  center  of 
lantern.     Allow  for  stage  of  tide  if  there  is  much 


THE  VESSEL'S  POSITION      67 

range.  Draw  the  safe  circle  with  S'  as  a  center. 
With  the  object  as  a  center  draw  a  second  circle 
tangent  to  the  outside  of  the  first  circle  at  E. 
Measure  the  distance  AE  on  the  chart.  With 
the  distance  AE  and  the  known  height  AB  the 
angle  AEB  can  be  computed.  Now  as  long  as  the 
angle  subtended  by  AB  is  smaller  than  the  angle 
AEB  the  vessel  will  pass  safely  outside  of  S'.  By 
similar  argument,  as  long  as  the  angle  subtended 
by  AB  is  greater  than  AGB  the  vessel  will  pass 
safely  inside  the  danger  S. 

Danger  Beaeings  are  useful  when  coasting  to 
warn  a  navigator  by  one  compass  bearing  when 
the  course  is  leading  into  danger.  Suppose  a  ves- 
sel is  steering  a  course,  as  shown  in  Figure  15, 
along  a  dangerous  coast  with  an  outlying  reef  as 
shown,  with  only  the  landmark  A  as  a  guide. 
Draw  through  A  a  line  AX  that  will  clear  the  dan- 
ger all  along.  Note  its  direction  by  the  compass 
rose.  Take  frequent  bearings  of  A.  As  long  as 
the  bearings  YA  and  ZA  are  to  the  right  of  XA 
the  vessel  is  on  the  safe  side  of  XA  and  clear  of 
danger.  If  a  bearing  taken  is  to  the  left  of  XA 
the  vessel  must  steer  off  shore. 

Although  the  object  in  sight  may  be  so  nearly 
ahead  as  to  be  valueless  for  a  definite  fix^  this 
method  may  be  employed  to  keep  the  vessel  out  of 
danger. 


68    SMALL  BOAT  NAVIGATION 


Ranges.     A  range  consists  of  two  well  charted 
objects  in  line  that  can  be  used  as  a  navigational 


Fig.  15. —  Danger  Bearing  and  Range. 

aid.     Thus  in  the  above  problem,  if  another  well 
charted  object  lies  in  the  prolongation  of  AX  as 


THE  VESSEL'S  POSITION      69 

at  B,  Figure  15,  the  line  XAB  is  called  a  range. 
It  is  unnecessary  to  take  the  bearings  YA  and  ZA 
in  this  case,  because  as  long  as  the  rear  object  is 
seen  to  the  left  of  A  (called  an  "open  range"), 
the  vessel  is  safe.  Ranges  are  used  a  great  deal 
in  river  and  harbor  work. 

The  course  to  be  steered  is  marked  by  two  ob- 
jects, which  when  kept  in  line  indicate  a  safe 
course  to  steer.  Sometimes  a  danger  will  lie  on 
one  side  of  the  range  with  good  water  on  the  other. 
This  constitutes  in  effect  a  danger  bearing. 
When  taking  cross  bearings  for  anchoring  it  may 
happen  that  one  of  the  bearings  will  be  on  a  range, 
which  can  be  plotted  directly  on  the  chart  without 
observing  its  direction.  Anchoring  on  ranges  in 
open  harbors  is  a  very  common  practice. 

If  in  a  strange  locality,  the  navigator  should 
observe  and  compare  the  compass  bearings  of  all 
ranges  with  the  bearings  indicated  on  the  chart  in 
order  to  make  certain  of  their  identity. 

Rounding  an  Object  at  a  Given  Distance. 
To  steer  an  arc  course  around  a  light  and  keep  it 
at  a  given  distance  without  the  use  of  "  fixes," 
provided  there  is  no  current,  stand  on  the  first 
course  until  the  light  is  at  the  desired  distance. 
Immediately  bring  the  light  abeam  and  steer  this 
new  course  until  the  light  is  one-half  point  abaft 
ihe  beam.     Now   change   course  until  the  light 


70    SMALL  BOAT  NAVIGATION 

bears  one-half  point  forward  of  the  beam  and  steer 
this  new  course  until  the  light  bears  one-half  point 
abaft  the  beam  again  and  repeat.  By  this 
method  the  vessel  travels  on  a  polygon,  the  in- 
scribed circle  of  which  has  a  radius  of  the  desired 
distance.  The  number  of  sides  of  the  polygon 
may  be  indefinitely  increased,  so  that  the  light 
may  be  rounded  by  frequently  changing  the  course 
just  enough  to  keep  the  light  abeam. 

The  Koch  Plotter.  Reference  has  been  fre- 
quently made  to  this  instrument  and  it  is  de- 
scribed here  instead  of  in  Chapter  2  because  its 
use  is  peculiarly  applicable  to  the  problems  here 
presented.  It  can  perform  all  the  functions  of 
the  compass  rose,  parallel  rulers,  three  arm  pro- 
tractor, etc.  By  using  this  instrument  all  the 
above  can  be  done  away  with.  The  writer  has  fre- 
quently used  it  and  would  not  go  to  sea  without 
one.  It  facilitates  the  solution  of  all  piloting 
problems  that  involve  bearings,  angles,  or  courses. 
It  is  simple  in  construction  as  the  following  de- 
scription indicates. 

All  materials  except  bolts  and  washers  are 
transparent.  There  are  two  celluloid  plates,  one 
7"  square  plate  with  two  series  of  lines  perpen- 
dicular to  each  other,  the  lines  of  each  series  being 
about  %"  apart,  the  other  a  7%"  circular  disc, 
marked  on  its  circumference  in  degrees.     These 


THE  VESSEL'S  POSITION      71 

are  centered  on  a  hollow  bolt  of  brass  and  can  be 
clamped  together  with  any  degree  of  friction  de- 
sired. Three  arms  are  placed  so  as  to  revolve 
around  the  hollow  bolt  and  can  be '  clamped  to- 
gether in  any  position  desired.     The  following  are 


16.—  Koch  Plotter. 


a  few  of  the  problems  that  can  be  solved  by  this 
ingenious  instrument.  (It  should  be  noted  that 
no  parallel  ruler,  or  other  instrument,  is  used,  and 
reference  is  not  made  to  the  compass  rose  on  the 
chart.) 


72    SMALL  BOAT  NAVIGATION 

(1)  To  set  a  given  course  from  a  given  posi- 
tion. Revolve  the  zero  mark  of  the  disc  to  the 
East  or  West  of  the  True  North  and  South  line 
of  the  square  an  amount  equal  to  the  compass 
error.  Set  one  arm  to  the  desired  compass  course. 
Lay  the  plotter  with  its  center  at  the  given  posi- 
tion. Revolve  the  plotter  about  this  position  as 
a  center  until  a  vertical  line  on  the  square  coin- 
cides with  a  meridian,  or  a  horizontal  line  with  a 
parallel  of  latitude.  The  course  now  lays  along 
the  bevel  edge  of  the  set  arm  and  can  be  drawn  if 
desired. 

(2)  To  find  the  course  between  two  positions. 
Set  the  disc  for  compass  error  as  before.  Center 
the  disc  on  one  position  and  revolve  it  as  before. 
When  a  vertical  or  horizontal  line  of  the  square  is 
in  coincidence  as  before,  swing  one  arm  so  its  bevel 
edge  passes  through  the  second  object.  Read  off 
the  course  where  this  bevel  edge  cuts  the  degree 
marked  disc. 

(3)  To  plot  the  position  from  two  bearings. 
Set  the  disc  for  compass  error  as  in  (1).  Set  the 
two  arms  to  the  two  compass  bearings  on  the  disc. 
Clamp  the  arms.  Manipulate  the  plotter  on  the 
chart  so  that  the  bevel  edges  of  these  two  arms 
pass  through  the  two  observed  objects  and  the 
vertical  lines  on  the  square  are  parallel  to  the 
meridians.     With   a   pencil   the   desired   position 


THE  VESSEL'S  POSITION     73 

can  be  marked  through  the  hollow  central  bolt. 
The  third  arm  can  now  be  swung  to  mark  a  new 
course  or  to  get  a  desired  compass  course  to  any 
object. 

(4)  To  plot  the  position  by  three  compass 
hearings  or  the  angles  between  three  objects.  In 
this  case  the  lines  on  the  square  plate  are  not 
brought  into  parallelism  with  the  meridians  on  the 
chart  because  the  compass  error  is  disregarded. 
Set  the  disc  to  zero  on  the  reference  line  of  the 
square  card.  Set  the  three  arms  to  the  compass 
bearings,  by  the  degrees  on  the  disc.  When  plot- 
ting by  observed  angles,  set  one  arm  at  zero,  the 
second  arm  by  degrees  on  the  disc  at  the  left  angle 
reading,  and  the  third  arm  by  degrees  on  the  disc 
to  a  reading  equal  to  the  sum  of  both  angles. 

Having  set  the  three  arms  by  either  of  the 
above  methods,  manipulate  the  plotter  on  the 
chart  until  the  bevel  edges  of  the  arms  intersect 
the  three  objects  on  the  chart,  the  center  arm 
being  on  the  center  observed  object.  Mark  the 
position  by  inserting  a  pencil  in  the  hollow  central 
bolt. 

(5)  To  get  the  compass  error  from  the  com- 
pass bearings  on  three  objects.  Proceed  as  in 
(4?).  Set  the  arms  to  the  compass  bearings  and 
get  the  position.  With  the  disc  set  at  zero  on  the 
reference  line  of  the  square  the  lines  on  the  square 


74    SMALL  BOAT  NAVIGATION 

will  not  now  be  in  parallelism  with  the  meridians 
on  the  chart  unless  the  compass  error  is  zero.  If 
not  parallel,  the  compass  error  can  be  found  as 
follows :  Keep  the  disc  in  its  position  on  the  chart 
and  revolve  the  square  until  its  lines  are  parallel 
to  the  meridians  of  the  chart.  The  angle  that 
now  shows  between  the  reference  line  of  the  square 
and  the  zero  of  the  disc  is  the  compass  error. 

Many  other  problems  can  be  solved  as  they 
arise.  The  principle  of  this  plotter  is  the  porta- 
ble compass  rose.  When  the  square  card  has  its 
lines  parallel  to  a  meridian  or  parallel  of  latitude, 
the  disc  is  in  effect  a  compass  rose.  By  adjusting 
the  disc  to  zero,  deviation,  or  compass  error,  the 
compass  rose  indicates  directions  per  compass, 
magnetic,  or  true,  respectively.  The  instrument 
is  a  combination  of  compass  rose,  parallel  rulers, 
and  three  arm  protractor. 


CHAPTER  IV 

DEAD    RECKONING 

CORRECTING  the  Compass  Course.  When 
navigating  by  dead  reckoning  all  courses 
are  reduced  to  true  courses.  The  method 
of  correcting  the  compass  course  to  obtain  the 
true  course  is  given  in  Chapter  III. 

The  Compass  error  is  the  algebraic  sum  of  the 
deviation  and  variation.  If  the  compass  error  is 
East,  apply  it  to  the  right  of  the  compass  course 
to  get  the  true  course;  if  West,  apply  it  to  the 
left  of  the  compass  course  to  get  the  true  course. 
When  applying  this  correction  imagine  that  you 
stand  in  the  center  of  the  compass  card.  Some 
compasses  are  marked  from  0°  to  360°,  while  oth- 
ers are  marked  from  0°  to  90°  from  the  North  and 
South  to  the  East  and  West.  Eight  problems 
follow  to  illustrate  compass  correction.  The  first 
solution  in  each  case  is  for  a  compass  of  the  first 
type,  the  second  solution  (in  parenthesis)  for  a 
compass  marked  in  the  second  manner. 

Prob.  1.  Compass  Course  75*  (NT^E),  Compass  error  +  6* 
(50  E). 
Find  true  course        Answer  80».     (NSCE.) 

75 


76    SMALL  BOAT  NAVIGATION 

Prob.  2.  Compass    Course    75°     (N75°E),    Compass    error 

—  5°   (5°W). 

Find  true  course.  Answer  70°.     (N70°E.) 

Prob.  3.  Compass    Course  150°     (S30°E),    Compass    error 
+  10°  (10°E). 

Find  true  course.  Answer  160°.     (S20°E.) 

Prob.  4.  Compass    Course  150°     (S30°E),    Compass    error 

—  10°  (10°W). 

Find  true  course.  Answer  140°.     (S40°E.) 

Prob.  5.  Compass    Course  220°    (S40°W),   Compass   error 
+  4°  (4°E). 

Find  true  course.  Answer  224°.     (S44°W.) 

Prob.  6.  Compass   Course  220°    (S40°W),   Compass   error 
—  4°  (4°W). 

Find  true  course.  Answer  216°.     (S36°W.) 

Prob.  7.  Compass   Course  305°    (N55°W),   Compass   error 
+  6°   (6°E). 

Find  true  course.  Answer  311°.     (N49°W.) 

Prob.  8.  Compass    Course  305°    (N55°W),   Compass   error 

—  6°  (6°W). 

Find  true  course.        Answer  299°.     (N61°W.) 

The  Sailings.  When  a  vessel  sails  from  one 
place  to  another  on  the  earth's  surface,  the  com- 
putations connected  therewith  involve  five  quanti- 
ties, viz. :  the  Course,  the  Distance,  the  Difference 
of  Latitude,  the  Departure,  and  the  Difference  of 
Longitude,  Solution  of  problems  involving  these 
quantities  is  called  Sailings,  There  are  many 
kinds  of  Sailings  employed  by  navigators,  of  which 
the  following  is  a  list. 

1.  Plane  Sailing. 

2,  Traverse  Sailing. 
S.  Spherical  Sailing. 


DEAD  RECKONING  77 

4.  Parallel  Sailing. 

6.  Middle  Latitude  Sailing. 

6.  Mercator  Sailing. 

7.  Great  Circle  Sailing. 

8.  Composite  Sailing. 

The  last  three  will  not  be  considered  as  they  are 
used  in  cases  where  the  distance  sailed  is  very 
large,  and  do  not  come  within  the  scope  of  this 
work.  Middle  Latitude  sailing  is  the  one  most 
used  in  Dead  Reckoning,  An  understanding  of 
the  first  four,  however,  is  necessary  to  an  under- 
standing of  Middle  Latitude  sailing,  and  they  are 
here  discussed  to  lead  up  to  Dead  Reckoning.  Al- 
though the  problems  of  Dead  Reckoning  can  be 
solved  by  trigonometry,  in  practice  they  are  solved 
by  the  use  of  Tables  1  and  £  of  Bowditch's  Useful 
Tables. 

The  curved  line  joining  any  two  places  on  the 
earth's  surface  and  cutting  all  meridians  at  the 
same  angle  is  called  the  Rhumb  Line,  The  con- 
stant angle  which  this  line  makes  with  the  meridi- 
ans is  called  the  Course;  the  length  of  the  line  be- 
tween any  two  places  is  called  the  Distance, 

Plane  Saiung.  For  the  moment,  suppose  the 
curvature  of  the  earth  is  neglected.  In  Figure  IT, 
T  is  the  point  of  departure,  T'  the  point  of  desti- 
nation, 'TF  is  the  rhumb  line.     Draw  Tn  and  T'n, 


78    SMALL  BOAT  NAVIGATION 

forming  a  right  angle.  Tn  is  the  meridian  and 
T'n  is  the  parallel  of  latitude.  nTT'  is  the 
course,  being  the  angle  the  rhumb  line  makes  with 
the  meridian.     TT'  is  the  distance  (Dist.),  being 


Fig.  17.—  Plane  SaUing. 


the  length  of  the  rhumb  line.  Tn  is  the  difference 
of  latitude  (DL)  and  T^'n  is  the  departure  (Dep). 
Then  from  the  right  triangle,  TT^n,  we  have  the 
following  formulae: 

Dep 

Dist 


Sin  C 


DEAD  RECKONING  79 

DL 


Cos  C  = 


Dist 

Dep 

Tan  C  = 

DL 

By  use  of  these  equations  all  problems  that  arise 
in  plane  sailing  can  be  solved,  trigonometrically. 

A  much  simpler  method  of  working  the  sailings 
is  by  the  use  of  Tables  1  and  2,  Bowditch.  These 
are  commonly  called  the  Traverse  Tables.  The 
tables  are  simply  solutions  of  right  triangles. 
Referring  to  any  page  of  Tables  1  or  2,  at  the  top 
(or  bottom)  of  the  page  is  the  course  or  angle,  C. 
The  three  quantities  found  on  any  one  line  are  the 
three  sides  of  the  triangle,  Distance,  Latitude,  and 
Departure.  By  entering  this  table  with  any  two 
known  quantities,  the  other  two  can  be  found  by 
inspection.     A  few  examples  will  make  this  clear. 

Example  1.  A  ship  sails  SSW,  250  miles.  Required  the 
difference  of  latitude  and  departure. 

Enter  table  1,  at  course  SSW.  It  occurs  on  top  of  page 
so  take  names  of  columns  from  top.  Under  the  column 
marked  Dist.  look  for  250.  On  the  same  line  is  the  solu- 
tion under  the  columns  marked  Lat.  and  Dep. 

Diff.  of  Lat.=  231  miles  =  231'=  3°—  51'  S. 

Dep.  95.7  miles  W. 

Example  2.  A  vessel  sails  880  E,  190  miles.  Find  the 
difference  of  latitude  and  departure. 

All  courses  are  figured  from  North  as  zero  right  around 


8o    SMALL  BOAT  NAVIGATION 

the  compass  in  a  clockwise  direction.  Therefore  S80  E 
is  the  equivalent  of  NlOO  E,  or  course  100.  Enter  Table  3 
at  the  course  100.  This  occurs  at  the  bottom  of  the  page 
so  take  all  column  names  from  the  bottom.  Opposite  DisL 
190  we  find 

Dep  =  187.1,  Lat  =  33,  therefore 
DL  =  33'S. 
Dep  =  187.1  miles  E. 

Example  3.  A  vessel  has  sailed  115  miles  to  the  North 
and  155  miles  to  the  West.  Required  the  Course  and  Dis- 
tance sailed  (using  table  1). 

In  this  case  Lat  =  115N  and  Dep  =  155W.  Enter  table 
1  and  find  a  course  where  115  and  155  are  found  abreast 
each  other  in  the  colunms  marked  Lat  and  Dep  respectively. 
This  occurs  most  nearly  at  4%  points;  the  angle  is  taken 
at  the  bottom  because  the  proper  names  of  the  columns 
occur  there.    Since  the  Lat  is  N  and  the  Dep  is  W  the 

Course  =  NW%W.    The  distance  is  found  on  the  same 
line  as  115  and  155,  and  in  this  case  is  193  miles. 

Example  4.  A  vessel  sails  67  miles  to  the  North  and  52 
miles  to  the  West.  Required  the  Course  and  Distance, 
using  table  2. 

In  this  case  Lat  =  67N  and  Dep  =  52W. 

Enter  table  2  and  find  the  page  where  the  known  quan- 
tities occur  on  the  same  line.    This  occurs  most  nearly  under 
32,    and    the    distance   is    79.    Since    the    proper    colimin 
names  occur  at  the  top  of  the  page,  the  result  is 
Course  =  N3^°W  =  328°. 
Distance  =  79  miles. 

Tea  VERSE  Saiung.  So  far  we  have  considered 
the  case  where  only  one  course  and  one  distance  is 
involved.  If  the  vessel  sails  several  different 
courses  and  distances,  these  can  all  be  reduced  to 
one  equivalent  course  and  distance  by  the  method 
of  traverse  sailmg.  This  is  done  by  finding  the 
difference  of  latitude  to  the  North  or  South  and 


DEAD  RECKONING 


8i 


the  departure  to  the  East  or  West  for  each  course 
and  distance  and  then  taking  the  algebraic  sum  of 
these  differences  of  latitude  and  departure  to  find 
the  equivalent  course  and  distance. 

Suppose  in  Fig.  18  that  the  vessel  has  sailed  the 
distance  AB  on  the  course  GAB  and  then  sailed 


Fio.  18.— Traverse  Sailing. 

the  distance  BC  on  the  course  DBC.  Its  final  pa« 
sition,  by  diagram,  is  the  same  as  though  it  had 
sailed  the  distance  AC  on  the  course  OAC. 

Considering  the  first  course  and  distance,  HA 
equals  the  corresponding  difference  of  latitude  and 
HB  the  corresponding  departure;  considering  the 
second  course  and  distance  DB  equals  the  corre- 
sponding difference  of  latitude  and  DC  the  corre- 


82     SMALL  BOAT  NAVIGATION 

spending  departure.  Add  the  differences  of  lati- 
tude. 

HA  +  DB  =  AO. 

and  add  the  departures 

HB  +  DC  =  OC. 

but  AO  and  OC  are  the  difference  of  latitude  and 
departure  respectively  for  the  course  OAC  and 
distance  AC. 

To  sum  up:  Starting  with  an  initial  position, 
A,  and  given  several  courses  and  corresponding 
distances,  the  final  position  C  is  arrived  at  by  add- 
ing the  several  differences  of  latitude  and  several 
departures  and  with  these  two  sums  proceeding  as 
in  plane  sailing. 

A  tabular  form  is  used  for  the  work  as  follows : 

Example.  A  vessel  sails  SSW,  12  miles;  SW,  40  miles; 
ESE,  5  miles;  E  by  N,  60  miles;  SE  by  S,  12  miles.  Find 
the  course  and  distance  made  good. 

This  is  solved  in  a  tabular  form  as  follows:  In  column 
1  place  the  courses,  in  column  2  the  distances,  in  columns 
3  and  4  the  Lats,  according  as  they  are  North  or  South, 
and  in  columns  5  and  6  the  Deps,  according  as  they  are 
East  or  West.  Next  take  the  difference  between  the  sums 
of  columns  3  and  4,  and  the  difference  between  the  sums 
of  columns  5  and  6,  in  each  case  retaining  the  names  of 
the  larger  quantity.  With  these  differences  as  the  equiv- 
alent Lats  and  Deps  enter  table  1  and  get  the  equivalent 
Course  and  Distance. 

Parallel  Sailing.  Thus  far  the  spherical 
form  of  the  earth  has  been  ignored.     It  has  only 


DEAD  RECKONING 


83 


Course 

Dist 

Lat 

Dept           1 

N 

8 

E 

W 

SSW 

U 

11.1 

4.6 

SW 

40 

29.3 

28.3 

ESE 

5 

1.9 

4.6 

E  by  N 

60 

11.7 

58.8 

SE  by  S 

19 

10.0 

6.7 

SE  1/4S 

53.5 

11.7 

51.3 
11.7 

70.1 
32.9 

32.9 

39.6 

37.2 

Form  for  Traverse  Sailing. 


been  considered  as  a  plane  surface,  and  Difference 
of  Longitude  has  not  been  taken  into  account. 
Problems  involving  Differences  in  Longitude  (ab- 
breviated DLo)  are  solved  by  Spherical  Sailing, 
of  which  Parallel  Sailmg  is  the  simplest  form. 
When  a  vessel  sails  upon  an  East  or  West  course 
a  certain  distance,  this  distance  is  the  departure. 
Converting  this  departure  into  degrees  and  min- 
utes of  longitude,  or  vice  versa,  is  done  by  parallel 
sailing. 

Suppose  in  Figure  19,  T  and  T'  are  two  places 
in  the  same  latitude;  P,  the  adjacent  pole;  TTT 
the  arc  of  the  parallel  of  latitude  between  the  two 
places  (is  the  departure) ;  MM',  the  correspond- 
ing arc  of  the  equator  intercepted  between  the  me- 
ridians passing  through  the  two  places  (is  the  dif- 


84    SMALL  BOAT  NAVIGATION 

ference  of  longitude) ;  CMM'  is  the  plane  of  the 
equator ;  CP  is  the  earth's  axis ;  TOT^  is  a  plane 


Fig.  19.— Parallel  Sailing. 

through  the  parallel  of  latitude  TT'.     Now  by 
construction 

TT'  =  Dep  MM'  =  DLo 

It  can  be  shown  trigonometrically  that 
DLo  =  Dep  sec  L 


DEAD  RECKONING  8$ 

This  formula  expresses  the  relation  between  de- 
parture in  miles  and  difference  of  longitude  in  min- 
utes. Problems  in  interconversion  of  Dep  and 
DLo  may  be  worked  by  the  above  formula.  A 
much  simpler  method  is  the  use  of  Traverse  Ta- 
bles. Since  the  Traverse  Tables  are  based  on  the 
formula  DL  =  Dist  cos  C,  we  may  substitute  the 
departure  for  the  column  marked  Lat,  and  the 
difference  of  longitude  for  that  marked  Dist,  and 
the  Latitude  for  the  courses  marked  at  the  top 
and  bottom  of  the  page.  The  tables  can  then  be 
used  to  these  conversions. 

Example.  A  vessel  in  Latitude  40°  sails  due  East  167 
miles.     Required  the  diflFerence  of  longitude. 

Enter  table  2  at  course  marked  40".  Under  column 
marked  Lat  find  167.  Pick  out  the  number  opposite  167 
in  the  column  marked  Dist  TTiis  is  the  required  diflFer- 
ence of  longitude  in  minutes,  in  this  case,  218'  or  3*  —  38'E. 

Example.  A  vessel  in  Latitude  20° — 30'  sails  due  West 
a  distance  of  140  miles.  Required  the  diflFerence  of  longi- 
tude. In  this  case,  since  these  tables  are  made  only  for  even 
degrees,  the  result  must  be  picked  out  for  Lats.  (courses  in 
Table)  20°  and  21°.  In  this  case  the  diflFerences  of  longi- 
tude are 

DLo  =  149.5  =  2°  SO^'W 

Middle  Latitude  Saiung.  When  a  vessel 
sails  on  other  than  an  East  or  West  course  on  a 
parallel  of  latitude,  its  latitude  is  constantly 
changing  and  the  Parallel  Sailing  method  of  in- 


86    SMALL  BOAT  NAVIGATION 

terconverting  departure  and  difference  of  longi- 
tude must  be  modified.  In  Figure  20,  T  is  the 
point  of  departure;  T'  the  point  of  destination; 


Fig.  20. —  Middle  Latitude  Sailing. 


P,  the  earth's  pole;  TT'  the  rhumb  track;  n'TT', 
the  course;  Tn  and  n'T^  the  respective  parallels 
of  latitude;  MM^  the  equator.     By  construction 


DEAD  RECKONING  87 

the  difference  of  longitude  is  MM'.  Now  draw  a 
parallel  of  latitude  LL'  halfway  between  Tn  and 
n'T'.  The  change  in  latitude  between  T  and  T'  is 
Tn'.  CaU  the  latitude  of  T  "  Lat  Lfeft,"  and  the 
latitude  of  T'  "  Lat  arrived  at,"  and  the  latitude 
of  LL',  "  Middle  Lat." 

Had  the  vessel  made  all  of  its  change  of  longi- 
tude along  the  line  Tn,  then  DLo  =  Dep  sec  (Lat 
Left).  If  it  had  all  been  made  along  the  line  n'T', 
then  DLo  =  Dep  sec  (Lat  arrived  at).  Since  the 
change  was  made  along  intermediate  lines,  neither 
formula  is  applicable.  It  can  be  shown  mathe- 
matically that  for  an  ordinary  day's  run  of  a  ves- 
sel the  formula  DLo  =  Dep  sec  (Middle  Lat) 
is  correct.  The  method  of  conversion  based 
upon  this  formula  is  called  Middle  Latitude  Sail- 
ing. 

Having  found  the  latitude  arrived  at,  from  the 
latitude  left  and  the  difference  in  latitude,  the 
mean  of  the  two  is  taken  and  the  solution  of  the 
problem  becomes  the  same  as  the  solution  for  Par- 
allel Sailing,  substituting  the  Middle  Latitude  for 
the  single  Latitude  used  therein. 

Example.  A  vessel  in  Latitude  ^3"  SCTN,  Long.  58"  61'W, 
sails  SE  by  S,  300  miles.  Required  the  latitude  and  longi- 
tude arrived  at. 

Entering  Table  1,  Bowditch,  Course  SE  by  S,  Dist  300, 
wc  find  Lat  240.4  S  (4°  09.4'),  Dep  166.7E.    Proceeding 


88     SMALL  BOAT  NAVIGATION 

Lat  left   . .  .42°  30.0'N   Long  left     SS**  51'  W 

DL 4°  09.4'S    DiflF.  Long  (DLo). 219.2'   3°  39.2'E 


Lat  arr  at  38°  20.6'N   Long.   arr.   at    55"  11.8'W 

45''  30.0' 


2)80"  50.6' 


Mid.   Lat    ..40"  25.3' 

First  find  the  new  latitude,  then  take  the  mean  of  the 
first  and  second  latitudes  for  the  Middle  Latitude  (40" 
25.3').     Enter  Table  2  with  the  middle  latitude  as  a  course. 

With  Mid.  Lat.  40°  as  course,  DLo  (under  Dist.  column) 
corresponding  to  a  Dept  (under  Lat  column)  of  166.7  is 
217.6;  with  Mid.  Lat  41"  as  course,  DLo  is  220.9.  The 
mean  value,  corresponding  to  401/2°  is  219.2. 

Dead  Reckoning  is  the  process  of  determin- 
ing at  any  instant  the  vessel's  position  by 
applying  the  course  and  distance  run  from  any 
previous  well  determined  position.  Having  once 
determined  the  vessel's  position,  the  position  at 
any  subsequent  time  may  be  found  by  applying  the 
difference  in  latitude  and  difference  in  longitude 
obtained  by  the  method  of  traverse  sailing  de- 
scribed in  this  chapter.  Positions  thus  obtained 
are  called  Dead  Reckoning  (abbreviated  D.R.)  po- 
sitions, or  positions  by  account. 

Positions  by  dead  reckoning  are  not  as  accurate 
as  those  by  observation  because  they  may  be  in- 
fluenced by  incorrect  estimate  of  distance  run,  bad 
steering,  incorrect  compass  error,  unknown  cur- 
rents, etc.,  and  for  this  reason  every  opportunity 


DEAD  RECKONING  89 

that  presents  to  fix  the  position  by  bearings  should 
be  grasped. 

To  obtain  the  vessel's  position  by  dead  reckon- 
ing it  is  necessary  to  have  some  previous  well  de- 
termined position.  When  a  vessel  leaves  port,  its 
position  is  always  accurately  determined  by  ob- 
servations on  the  last  well  charted  navigational 
mark  that  is  seen.  This  is  called  taking  the  de- 
parture. 

Taking  the  Departuee.  This  departure  must 
not  be  confused  with  departure  used  in  finding  the 
difference  of  longitude.  Takmg  the  departure 
consists  of  obtaining  a  good  "  fix,"  that  is  an  ac- 
curately plotted  position,  from  which  future  posi- 
tions by  dead  reckoning  are  computed.  It  is  gen- 
erally done  by  bearings  on  a  well  charted  object. 
There  are  two  methods  of  using  this  departure. 
By  the  first  method  the  vessel's  position  is  plotted 
on  the  chart,  by  any  of  the  methods  described  in 
Chapter  3,  and  the  latitude  and  longitude  of  this 
position,  taken  from  the  chart,  are  used  as  the  de- 
parture for  future  reckoning.  In  the  second 
method,  the  bearing  and  distance  are  found  of  the 
object  used  for  departure.  The  latitude  and  lon- 
gitude of  the  object  are  taken  as  the  point  of  de- 
parture for  future  reckoning,  and  the  course  and 
distance  from  the  object  to  the  vessel  (the  reverse 
of  its  bearing)  at  this  time  are  entered  as  the  first 


90    SMALL  BOAT  NAVIGATION 

course  and  distance  in  the  dead  reckoning  col- 
umns. The  course  from  the  object  to  the  vessel  is 
the  reverse  of  the  bearing  of  the  object  from  the 
vessel. 

To  make  this  clear,  suppose  bearings  are  taken 
on  a  light  and  plotted  on  the  chart,  and  that  the 
position  thus  obtained  is  Lat  41°  16'N,  Long  70° 
60'W.  This  would  be  the  point  of  departure  ac- 
cording to  the  first  method  and  dead  reckoning 
positions  would  be  computed  from  this.  If,  how- 
ever, a  light  whose  position  were  Lat  41°  20'N, 
Long  70°  SOW,  bore  North  true,  Dist  4  miles, 
then  the  position  of  the  light  can  be  taken  as  the 
point  of  departure,  and  the  course  South  (reverse 
of  bearing)  true,  and  the  Dist  4,  are  entered  in  the 
dead  reckoning  columns  ahead  of  the  first  course 
and  distance  run  by  the  vessel.  In  either  case  the 
result  is  the  same. 

Current,  The  Set  of  a  Current  is  the  direction 
toward  which  it  is  moving. 

The  Drift  of  a  Current  is  the  speed  per  hour 
with  which  it  moves. 

When  a  vessel  is  sailing  in  a  current,  the  set  and 
drift  of  which  can  be  determined  with  any  ac- 
curacy, as  in  the  Gulf  Stream,  allowance  for  the 
current,  when  figuring  dead  reckoning,  should  be 
made  as  follows: 

Enter  the  set  of  the  current  in  the  column  of 


DEAD  RECKONING  91 

courses.  Multiply  the  drift  of  the  current  by  the 
number  of  hours  run,  and  enter  this  opposite  the 
set  in  the  column  of  distances.  The  eflPect  of  the 
current  on  a  vessel  is  the  same  as  though  the  ves- 
sel actually  sailed  the  set  and  drift. 

Summary.  To  sum  up  the  subject  of  dead 
reckoning,  a  problem  is  given  herewith  that  illus- 
trates departure  by  the  second  method,  traverse 
sailing,  compass  error,  and  allowance  for  current. 

Example.  Took  departure  at  8  a.m.  on  Cape  Charles 
Lightship  (Lat  37"  05'N,  Long  75°  43'W)  bearing  (p.s.c— 
per  standard  compass)  271**,  Dist  8  miles,  ship's  head  Eaist 
(p.s.c.),  var.  — 5",  dev.  — 4°  (this  gives  true  bearing  of 
light  ship  262*).  Thence  sailed  until  10  p.m.  on  courses  as 
follows. 

Course  (p.s.c.)  110®,  var.  —5**,  dev.  —6®,  distance   6    miles 

»  "         84**      "    5** 

n  »»  790'     ,,     _5o| 

»»       286**,     "    —6% 

The  known  current  is  estimated  at  aet  48  (true),  drift  .5 
knot  per  hour.  Find  Lat  and  Long  at  10  p.  m.  by  dead 
reckoning. 

Solution:  The  current  for  14  hours  at  .5  knot  per  hour 
is  7  miles,  totaL     (See  next  page  for  table). 

Lat   left    37.°— 05'   N      Long   left    ....75^—43'    W 

DL  65.2'    F—  05.2'N      D   Lo    9.8'E 


-6^c 

Ustan 

ice   6 

-4% 

» 

8 

-4^ 

w 

10 

-3% 

>» 

15 

+  1% 

n 

40 

+  3% 

yy 

48.5 

+  8% 

» 

5 

Lat   10  P.M.    ..Sa**— 10.2'N      Long  10  p.m.  .75**— 33.2'W 

Day's  Run.     It  is  customary  to  calculate  the 
total  run  for  the  preceding  24  hours  every  day 


92    SMALL  BOAT  NAVIGATION 


as     V 


N 


E 


W 


(Bearing  of  Lightship)  82° 

8 

1.1 

7.9 

110°   —5°  —6°  —11°     99° 

6 

0.9 

5.9 

84°   —5°  —4°  —    9°     75° 

8 

2.1 

7.7 

79°   —5°  —4°  —   9°     70° 

10 

3.4 

9.4 

67.°   —5°  —3°  —   8°     59° 

15 

7.7 

12.9 

20°  —6°   +1°  —    5°     15° 

40 

38.6 

10.4 

^6°  —  6°  +  3°  —    3°  283° 

48.5 

10.9 

47.2 

240°  —  7°  +8°  -f-     1**  241° 

5 

2.4 

4.4 

(Current)                           48° 

7 

4.7 

5.2 

68.5 
3.3 
65.2N 

3.3      59.4 
51.6 
=  DL  7.8E 

51.6 
=  Dep 

at  noon.  Having  the  vessel's  positions  at  two 
succeeding  noons  the  problem  resolves  itself  into 
finding  the  course  and  distance  made  good  be- 
tween the  two  positions. 

Example.  The  position  of  a  vessel  at  noon  of  July  12, 
1914,  is  Lat  35°—  lO'N,  Long  134°—  Ol'W,  on  July  13,  1914, 
the  vessel's  position  is  Lat  36°— 03'N,  Long  131°— 14' W. 
Find  the  course  and  distance  made  good. 

Pos.    July    13....36°— 03'N  131°— U'W 

Pos.    July    12....35°— lO'N 134°— Ol'W 


Run 


53'N   ..D  Lo    2°— 47'E  =  167'E 


Middle  Lat  =  36°  approximately,  D  Lo  =  167'.  From 
Table  2,  Dep  =  135.1.  Entering  Table  2  with  Lat  53  (which 
is  D  L  above),  and  Dep  =  135.1,  we  obtain 

Course  OSVi* Distance  146  miles,  made  good. 


DEAD  RECKONING  93 

Graphic  Soltttion  op  Dead  Reckoning.  A 
much  quicker  solution  of  a  vessel's  run  by  dead 
reckoning  can  be  made  graphically  on  the  chart. 
From  the  point  of  departure  draw  the  true  course 
on  the  chart.  Measure  from  the  point  of  de- 
parture the  distance  run  on  this  course.  From 
this  second  point  draw  the  second  course  on  the 
chart  and  lay  oflP  from  this  second  point  the  dis- 
tance run  on  the  second  course.  By  continuing 
this  process  the  vessel's  position  by  dead  reckon- 
ing at  any  instant  can  be  obtained.  This  affords 
an  excellent  check  to  the  computations. 


PART  II 
SEAMANSHIP 


CHAPTER  V 

SOUNDINGS,    TIDES,    ETC. 

APPROACHING  LAND 

SOUNDINGS  are  taken  for  two  general  pur- 
poses :  first,  when  in  shallow  water,  to  ascer- 
tain that  there  is  sufficient  depth  of  water 
for  the  immediate  movement  of  the  ship,  and  to 
check  the  depths  as  given  on  the  chart ;  second,  to 
verify  dead  reckoning  positions  when  on  soundings 
in  a  fog  or  when  land  is  not  in  sight. 

The  best  aids  to  navigation,  when  running  in  a 
fog,  are  the  sounding  machine  and  the  hand  lead, 
and  the  navigator  should  make  every  possible  use 
of  them.  Even  in  clear  weather  the  sounding  ma- 
chine, or  deep  sea  lead  in  lieu  thereof,  may  be  of 
great  aid  to  the  navigator  in  verifying  h»  posi- 
tion. This  is  especially  true  when  making  a  land- 
fall. The  lead  and  line,  and  the  deep  sea  lead  and 
line  are  described  in  Chapter  2. 

The  Sounding  Machine.^     This  machine  pos- 

1  Whereas,  a  Sounding  Machine  will  only  be  found  on  a 
large  yacht  navigated  by  a  licensed  Master,  it  is  still  con- 
sidered of  sufficient  importance  to  merit  a  short  description. 

97 


98    SMALL  BOAT  NAVIGATION 

sesses  advantages  over  the  deep  sea  lead,  for 
which  it  is  a  substitute,  in  that  soundings  can  be 
obtained  at  great  depths  and  with  accuracy  and 
rapidity  without  stopping  the  ship.  It  consists 
of  a  stand  on  which  is  mounted  a  reel  which  holds 
the  sounding  wire.  Crank  handles  are  fitted  to 
the  reel  for  reeling  in  the  wire  after  a  sounding 
has  been  taken,  and  a  suitable  brake  controls  the 
reel  when  the  wire  is  running  out  to  take  a  sound- 
ing. The  lead  is  secured  to  the  outer  end  of  the 
wire.  Its  base  is  hollow  to  receive  tallow  for  arm- 
ing. Attached  to  the  sounding  wire,  just  above 
the  lead,  is  the  depth  registering  instrument  en- 
closed in  a  hollow  cylindrical  case.  Various  reg- 
istering devices  are  in  use,  but  all  depend  upon 
the  increasing  pressure  of  water  at  increasing 
depth. 

The  Lord  Kelvin  Machine  employs,  for  its  reg- 
istering device,  a  slender  glass  tube,  sealed  at  one 
end  and  open  at  the  other.  This  is  coated  inside 
with  a  chemical  preparation  which  changes  color 
on  contact  with  sea  water.  This  tube  is  placed, 
closed  end  up,  in  the  metal  container.  When  tak- 
ing a  sounding,  as  the  lead  sinks,  taking  the  regis- 
tering device  with  it,  the  air  contained  in  the  glass 
tube  is  compressed  with  a  force  dependent  upon 
the  depth.  Salt  water  enters  the  open  end  as  the 
air  is  compressed,  and  this  makes  a  clearly  de- 


SOUNDINGS,  TIDES,  ETC,     99 

fined  line  of  discoloration  a  distance  from  the  open 
end  dependent  on  the  depth.  A  scale  is  provided 
upon  which  the  depth  can  be  measured  by  this 
mark  of  discoloration. 

Ground  glass  tubes  may  be  substituted  for  the 
chemically  prepared  ones.  When  a  ground  glass 
tube  is  wet,  it  shows  clear  over  the  wetted  surface. 
Such  tubes  can  be  used  an  indefinite  number  of 
times,  if  thoroughly  dried  each  time. 

Mechanical  depth  recorders  can  be  substituted 
for  the  glass  tubes.  In  such  a  device  water  pres- 
sure acts  upon  a  piston  against  the  pressure  of  a 
graduated  spring,  and  the  depth  is  recorded  on  a 
scale  by  an  index  pointer  that  is  moved  by  the 
piston. 

When  Making  Land  in  a  Fog  the  sounding  ma- 
chine, or  deep  sea  lead,  must  be  kept  going  at  half 
hour  intervals  for  some  hours  before  it  is  expected 
that  soundings  can  be  obtained.  Several  sound- 
ings at  irregular  intervals  are  worse  than  useless 
as  they  give  no  definite  information  and  may  lead 
to  disaster.  In  using  the  sounding  machine,  be 
careful  not  to  invert  the  tube  when  withdrawing  it 
from  the  tube  case,  as  that  would  cause  water  to 
run  toward  the  closed  end  of  the  tube,  causing  a 
discoloration  and  hence  a  false  reading.  The  lead 
must  be  freshly  armed  at  each  cast.  Having 
picked  up  the  bottom,  the  navigator  can  proceed 


100    SMALL  BOAT  NAVIGATION 

as  described  under  **  Piloting  by  Soundings  in  a 
Fog," 

Keep  a  sharp  lookout  for  any  landmarks  that 
may  appear  during  a  momentary  lifting  of  the 
fog,  and  listen  carefully  for  signals.  If  a  fag 
signal  is  heard,  the  landmark  where  it  is  situated 
can  be  determined  by  reference  to  the  Light  List, 
which  gives  the  characteristics  of  all  fog  signals 
(viz:  the  number  and  duration  of  the  blasts).  If 
approaching  land  and  the  soundings  indicate  a 
dangerous  proximity  to  land,  if  no  signals  have 
been  heard  that  will  further  aid  navigation,  the 
only  safe  course  is  to  anchor  or  stand  off  shore. 
When  running  slowly  in  a  fog  (as  the  law  re- 
quires) it  must  be  borne  in  mind  that  the  relative 
effect  of  current  is  increased.  Sometimes,  when 
approaching  a  bold  bluff  shore,  a  vessel  may  be 
warned  of  its  proximity  by  having  its  own  fog  sigj 
nals  echoed  back  from  the  cliff.  In  some  inland 
waters  where  cliffs  are  frequent,  navigators  de- 
pend upon  this  to  a  great  extent. 

Piloting  by  Soundings  in  a  Fog.  Soundings 
taken  in  a  fog  serve  a  much  more  important  func- 
tion than  merely  to  give  the  depth  of  water  at  any 
one  position.  The  vessel's  position  can  often  be 
found  by  a  series  of  soundings.  In  thick  weather, 
when  approaching  or  running  close  to  land,  or  in 
inland  waters,  soundings  should  be  taken  contimi- 


so UNDINGS,  TIDES,  EtO:    ibi 

ously  and  at  regular  intervals,  and  the  character 
of  bottom  should  be  noted.  By  laying  off  the 
soundings  on  tracing  paper  along  a  line  that  rep- 
resents the  track  of  the  ship  and  to  d  scale  (dis- 
tances between  soundings)  corresponding  to  the 
scale  of  the  chart  and  then  moving  the  tracing 
paper  on  the  chart  so  that  the  courses  plotted  are 
parallel  to  corresponding  directions  on  the  chart 
until  the  observed  soundings  agree  with  the  chart 
soundings,  the  vessel's  position  can  generally  be 
well  determined.  While  some  waters  by  the  quick 
changes  in  soundings  along  the  bottom  adapt 
themselves  more  readily  than  others  to  this 
method,  there  are  few  places  where  the  navigator 
cannot  at  least  keep  out  of  danger  by  these  indi- 
cations. When  the  navigator  can  no  longer  de- 
termine with  some  degree  of  accuracy  that  his 
course  leads  clear  of  danger,  it  is  time  to  anchor 
until  more  favorable  conditions  present  themselves. 
To  illustrate  the  above  by  a  simple  example: 
Suppose  the  vessel  is  making  12  knots  over  the 
ground,  and  that  she  has  steered  East  for  30  min- 
utes and  then  NE  for  30  minutes.  Suppose  that 
soundings  have  been  taken  at  five  minute  intervals 
as  follows:  6,  7,  8,  7,  12,  8,  10  (when  course  was 
changed),  9,  7,  6,  8,  6,  10,  fathoms.  On  tracing 
paper  lay  off,  as  in  Figure  21,  to  the  scale  of  the 
chart,  AB  =  6  miles,  BC  =  6  miles  (30  minute 


I02    SMALL  BOAT  NAVIGATION 


runs  at  12  knots),  and  ABC  =  135°  (angle  be- 
tween courses).  This  represents  the  track  of  the 
vessel.  Now  divide  AB  and  BC  each  into  6  equal 
parts.  These  are  one  mile  intervals  and  the  divi- 
sion points  represent  the  positions  at  which  the 
soundings  were  taken.  Mark  the  soundings  at  the 
proper  division  points,  and  move  the  tracing  pa- 


-^A./-l 


Fig.  91. —  Piloting  by  Soundings. 


per  over  the  chart,  always  keeping  the  line  AB  in 
the  East  and  West  line  of  the  chart.  At  some 
portion  of  the  chart  it  will  be  found  that  the  depths 
on  the  tracing  paper  correspond  to  depths  on  the 
chart  (if  the  soundings  have  been  carefully  taken) 
and  the  vessel's  position  is  at  the  point  of  the  last 
sounding. 

Orienting  the  tracing  paper  is   facilitated  by 
drawing  a  few  meridians,  K,  L,  M,  N,  thereon.     If 


SOUNDINGS,  TIDES,  ETC.     103 

there  is  much  range  to  the  tide  the  stage  of  the 
tide  must  be  noted  when  soundings  are  taken  and 
allowance  must  be  made  for  the  height  of  tide. 
The  soundings  on  the  chart  are  for  mean  low 
water. 

Effect  of  Wind  and  Barometee  on  Sound- 
ings. When  navigating  waters  where  the  depth 
exceeds  the  vessel's  draft  by  only  a  small  amount, 
it  must  be  borne  in  mind  that  a  strong  wind  or 
unusually  high  barometer  may  cause  the  water  at 
low  tide  to  fall  below  the  depth  indicated  on  the 
chart. 

Piloting  Among  Coral  Reefs.  When  pilot- 
ing among  coral  reefs  or  banks,  a  time  should  be 
chosen  when  the  sun  is  astern.  Conning  should  be 
done  from  an  elevated  position  forward.  When 
the  observer  is  high  up,  the  line  of  demarcation  be- 
tween a  reef  or  shoal  and  deep  water  is  very 
clearly  seen. 

When  passing  between  shoals  or  dangers  where 
there  are  no  well  charted  navigational  marks  a 
mid-channel  course  should  be  steered.  Too  much 
emphasis  cannot  be  laid  upon  this  point.  Do  not 
save  seconds  by  passing  close  to  a  danger  when  a 
safe  course  offers.  Steering  a  mid-channel  course 
by  eye  is  a  simple  matter,  as  the  eye  can  make  a 
close  estimate  in  a  case  of  this  kind. 


104    SMALL  BOAT  NAVIGATION 

TIDES 

To  an  observer  tides  present  themselves  in  two 
different  manners,  by  alternate  elevation  and  de- 
pression of  the  water  level,  and  by  alternate  in- 
flows and  outflows  of  streams.  Properly  speaking 
tides  should  refer  to  the  vertical  motion  and  tidal 
currents  to  the  horizontal  flows.  However,  popu- 
lar usage  ascribes  both  these  meanings  to  tides. 

When  the  water  has  reached  a  maximum  level  it 
is  called  high  tide,  or  high  water.  When  it  has 
reached  a  minimum  level  it  is  called  low  tide,  or 
low  water.  The  interval  at  high  and  low  water, 
when  there  is  no  perceptible  movement,  is  called 
the  stand. 

Between  low  and  high  water,  when  the  tide  is 
setting  from  the  sea  toward  the  land,  the  horizon- 
tal movement  is  called  flood  tide.  When  the  hori- 
zontal movement  sets  from  the  land  toward  the 
sea,  between  high  and  low  water,  it  is  called  ehh 
tide.  The  interval  of  change  between  flood  and 
ebb,  when  there  is  no  perceptible  horizontal  move- 
ment, is  called  the  slack. 

The  Cause  of  the  Tides  is  the  difl^erence  in  the 
attraction  of  the  moon  (and  to  a  less  degree  of  the 
sun)  upon  the  various  unit  masses  of  water  and 
the  attraction  of  the  moon  on  the  earth  itself. 
This  diff^erence  of  attraction  combined  with  the 


SOUNDINGS,  TIDES,  ETC.     105 

relative  periodic  movements  of  the  moon  and  earth 
produce  the  periodic  ocean  disturbances  known  as 
tidal  phenomena. 

Establishment,  The  moon  being  the  dominant 
factor  in  tide  production,  it  is  apparent  that  the 
phenomena  should  bear  some  relation  to  the  lunar 
month  (28  days).  High  and  low  water  occur,  on 
the  average  of  these  28  days,  at  about  the  same 
intervals  after  the  transit  of  the  moon  over  the 
meridian.  These  nearly  constant  intervals,  ex- 
pressed in  hours  and  minutes,  are  known  re- 
spectively as  the  high  water  lunitidal  interval 
and  the  low  water  lunitidal  interval.  The  in- 
terval between  the  moon's  meridian  passage  at  any 
place  and  the  time  of  the  next  succeeding  high 
water,  as  observed  on  the  days  when  the  moon  is 
at  full  and  change  (new),  is  called  the  establish' 
ment;  it  is  also  spoken  of  as  the  time  of  high  water 
on  full  and  change  days  (abbreviated  "  H.  W.  F.  & 
C"),  for  since  the  moon's  meridian  passage  on 
these  days  occurs  at  midnight  and  noon  (of  the 
lunar  day),  the  establishment  is  approximately 
the  time  of  high  water.  If  to  the  time  of  high 
water  we  add  or  subtract  6  hours  31  minutes  (1/4 
of  a  lunar  day)  the  result  will  be  the  time  of  low 
water. 

Range,  Spring  and  Neap  Tides,  The  range  of 
a  tide  is  the  difference  in  height  between  high  and 


io6    SMALL  BOAT  NAVIGATION 

low  water.  At  new  and  full  moon  the  sun  and 
moon  produce  high  tides  at  the  same  times.  The 
effect  of  the  sun  augments  that  of  the  moon  and 
the  resultant  high  tides  are  higher  than  the  aver- 
age. Similarly  the  low  tides  are  lower  than  the 
average,  and  the  range  of  tides  is  greater.  Tides 
at  this  season  are  called  spring  tides.  At  the  time 
of  first  and  third  quarters  of  the  moon  the  high 
tides  due  to  the  moon  occur  simultaneously  with 
the  low  tides  due  to  the  sun.  The  resultant  high 
and  low  tides  are  less  than  the  average  and  the 
range  is  at  its  minimum.  Tides  occurring  at  this 
season  are  called  neap  tides.  Tidal  currents 
(flood  and  ehh)  are  strongest  at  spring  tides  and 
weakest  at  neap  tides. 

Tidal  Currents.  It  must  be  remembered  that 
the  periods  of  -flood  and  ehh  in  any  locality  are 
not  necessarily  coincident  with  the  periods  of  rise 
and  fall  of  the  tide.  The  inward  set  of  the  sur- 
face current  does  not  always  cease  when  the  water 
has  attained  its  maximum  height.  Local  condi- 
tions may  be  such  that  flood  may  continue  after 
high  water  has  been  reached,  or  vice  versa. 

This  may  be  more  apparent  by  comparing  two 
tidal  basins,  one  having  a  large  open  entrance  and 
the  other  having  a  narrow  restricted  opening.  In 
the  first  case  the  process  of  filling  and  emptying 
the  basin  keeps  pace  with  the  outside  sea  level  and 


SOUNDINGS,  TIDES,  ETC.     107 

ebb  and  fall,  flood  and  rise,  occur  at  practically 
the  same  time.  In  the  second  case  the  restricted 
entrance  retards  filling  the  basin  so  that  the  height 
of  water  without  may  reach  a  maximum  long  be- 
fore the  basin  fills.  In  this  case  flood  contmues, 
possibly  hours,  after  high  water  occurs,  and  in  a 
like  manner  the  restriction  will  cause  ebb  to  con- 
tinue long  after  low  water  has  occurred  outside. 

Times  of  High  and  Low  Water,  The  simplest 
and  quickest  method  of  obtaining  the  times  of  high 
and  low  water  and  other  tidal  data  is  by  use  of  a 
Tide  Table.  One  is  published  by  the  U.  S.  Coast 
and  Geodetic  Survey  annually,  and  gives  the  times 
of  high  and  low  water  at  many  seaports.  From 
these  others  may  be  deduced.  Much  other  tidal 
data  is  given  in  this  publication.  The  daily  pa- 
pers of  many  marine  ports  give  the  times  of  the 
tides  for  several  days  ahead  of  the  date  of  issue. 

When  no  tidal  table  or  data  is  obtainable  the 
time  of  high  water  can  be  computed  by  use  of  the 
Nautical  Almanac  as  follows :  To  the  time  of  the 
moon's  meridian  passage  add  the  lunitidal  interval 
(H.  W.  F.  &  C),  obtained  from  the  chart  or  from 
Bowditch's  Useful  Tables. 

The  time  of  the  moon's  meridian  passage  is  ob- 
tained as  follows:  From  the  Nautical  Almanac 
pick  out  the  Greenwich  Mean  Time  of  the  Upper 
Transit  of  the  Moon  at  Greenwich  for  the  local 


io8    SMALL  BOAT  NAVIGATION 

date  (Page  IV).  Also  pick  out  the  daily  varia- 
tion on  the  same  line.  With  this  'variation  and 
with  the  Longitude  as  arguments  enter  table  11, 
Bowditch,  and  obtain  the  correction  to  be  applied 
to  the  G.  M.  T.  of  Greenwich  Transit.  The  result 
is  the  Local  Mean  Time  of  the  moon's  meridian 
passage.  Now  add  to  this  the  time  of  H.  W.  F.  k 
C.  and  the  result  is  the  Local  Mean  Time  of  high 
water.  This  can  be  converted  to  Standard  time 
by  applying  the  difference  in  time  between  the  lon- 
gitude of  the  place  and  the  Standard  Meridian. 

Appendix  IV,  Bowditch,  contains  the  mean  luni- 
tidal  interval  of  high  and  low  water  for  many 
places.  The  charts  give  the  establishments  of 
many  ports  with  sufficient  accuracy  for  this  work. 

General,  To  sum  up,  when  approaching  land 
or  harbor,  the  navigator  must  know  the  draft  of 
the  vessel.  He  must  make  himself  familiar  with 
every  detail  of  the  charts  he  will  use,  and  must 
form  a  mental  picture  of  the  land  and  aids  to  navi- 
gation that  he  will  sight.  Allowance  must  be 
made  for  the  effect  of  the  position  of  the  sun  or 
moon  on  the  appearance  of  objects  sighted.  He 
must  be  familiar  with  the  characteristics  of  all 
lights,  buoys,  fog  signals,  and  other  aids  to  navi- 
gation that  he  will  use,  and  with  the  state  of  the 
tide  and  currents  in  channels  he  will  navigate.  He 
should  select  beforehand  the  objects  that  he  will 


SOUNDINGS,  TIDES,  ETC.     109 

use  for  bearings.  He  should  carefully  check  all 
buoys  to  prevent  confusion.  Ranges  should  be 
selected  and  lines  drawn  to  indicate  safe  courses 
and  danger  bearings  where  possible.  The  track 
of  a  vessel  entering  port  should  be  laid  down  on  a 
chart  before  entering,  and  this  should  be  carefully 
inspected  to  see  that  it  leads  clear  of  all  possible 
danger. 

The  vessel's  position  must  be  frequently  plotted 
on  the  chart  and  should  never  be  in  doubt  for  an 
instant.  Soundings  should  always  be  taken  when 
on  soundings,  whether  the  weather  be  clear  or 
cloudy.  The  navigator  should  familiarize  himself 
with  the  Inland  Rules  of  the  Road  given  in  Chap- 
ter 8  before  entering  pilot  waters. 


CHAPTER  VI 

MGHT  AND  BUOY  SYSTEM  OF  THE  UNITED  STATES 
LIGHTS 

LIGHTS  are  distributed  along  the  coast,  at 
harbor  entrances,  in  harbors,  and  at  other 
points  to  aid  navigation.  They  may  be 
placed  in  lighthouses,  on  lightships,  or  on  buoys. 
When  in  lighthouses,  there  is  generally  one  light 
to  a  house;  when  on  lightships  there  is  generally 
more  than  one. 

Lights  are  classified  as  fixed,  flashing,  intermit- 
tent, revolving,  and  fixed  and  flashing.  This  is 
necessary  so  that  when  a  light  is  sighted  it  can  be 
identified.  It  is  obvious  that  if  all  lights  were  the 
same,  the  navigator  might  become  confused  when 
approaching  land  if  his  position  were  at  all  un- 
certain. 

A  Fixed  Light  is  one  that  shows  uninterrupt- 
edly at  all  times. 

A  Flashing  Light  is  one  that  shows  a  short  flash 
and  is  then  occulted  for  a  long  interval. 

An  Intermittent  Light  is  one  that  shows  a  long 
flash  and  is  occulted  for  a  period  shorter  than  the 
flash. 

110 


LIGHT  AND  BUOY  SYSTEM    iii 

A  Revolving  Light  is  one  that  gradually  in- 
creases in  intensity,  then  gradually  decreases  in 
intensity  until  it  is  occulted,  and  then  gradually 
increases  again. 

A  Fixed  and  Flashing  Light  is  a  combination 
of  the  first  two. 

Lights  may  be  red  or  white  in  color.  As  stated 
before,  the  lights  are  given  different  characteris- 
tics so  that  they  may  be  readily  distinguishable. 
Flashing  lights  sometimes  flash  a  number  for  this 
purpose.  Generally  speaking,  main  coast  lights 
are  white,  although  there  are  exceptions  to  this 
rule.  Harbor  lights  may  be  white  or  red.  Red 
lights  are  used  to  mark  dangers,  such  as  ends  of 
breakwaters,  etc. 

Red  Sectors,  Many  white  lights  have  red  sec- 
tors, that  is,  the  light  shows  white  over  part  of  the 
horizon,  and  red  over  other  parts.  Red  sectors 
are  used  to  mark  dangers.  In  this  case  the  light 
shows  white  as  long  as  the  observer  is  in  safe  navi- 
gable waters,  but  when  in  the  same  sector  as  a 
shoal  or  other  danger  the  light  shows  red.  In  this 
case  the  vessel  is  safe  as  long  as  it  is  in  the  white 
sector. 

Light  Lists,  The  United  States  is  divided  into 
a  number  of  lighthouse  districts.  A  list  of  lights 
is  published  by  the  Hydrographic  Office  for  each 
district,  and  is  sent  on  request  to  any  ship  cap* 


112    SMALL  BOAT  NAVIGATION 

tain.  These  lists  include  all  authorized  lights, 
with  their  description,  etc.  Lights  in  lighthouses 
are  described  in  the  light  lists  as  follows:  (An 
example  is  taken  from  a  list.) 

"  Lighthouse  color,  white ;  foundation  brown ; 
lantern  yellow.  (This  is  to  identify  it  by 
day.) 

"  Hexagonal  screw-pile  structure ;  light  44  feet 
above  high  water. 

"  Bearings.  (Here  its  bearings  from  other  well 
charted  objects  are  given.) 

"  Character,  3000  candlepower,  red,  visible  8^ 
miles  (for  a  height  of  eye  of  15  feet  above  the  sea 
level). 

"  Fog  Signal.  (Here  a  description  of  the  fog 
signal  installed  at  the  light  is  given.)" 

Light  Vessels  are  moored  at  sea  outside  of  im- 
portant harbors,  and  on  the  edge  of  important 
shoals  on  the  coast  where  it  is  impracticable  to 
plant  lighthouses.  They  are  described  in  the 
same  light  list.  The  names  of  the  light  vessels 
are  painted  on  their  sides.  These  names  are 
taken  from  the  shoal  that  the  light  guards,  or 
from  other  sources.  Numbers  are  often  used  in 
lieu  of  names.  The  description  of  a  light  vessel 
from  the  light  list  is  given  as  follows : 

"  Description,  white ;  masts  yellow ;  topmast 
and  day  marks  black. 


LIGHT  AND  BUOY  SYSTEM     113 

**Rig.  2  masts,  schooner  rigged,  oval  day 
marks  at  each  mast  head. 

"  Bearings.  (Here  follow  the  bearings  of  the 
light  from  well  charted  objects.) 

"  Fog  Signal,  on  whistle,  blast  of  3  seconds,  si- 
lent 60  seconds,  blast  of  S  seconds,  silent  60  sec- 
onds, etc. 

"If  the  whistle  is  out  of  order  the  signal  is 
made  on  the  bell  as  follows:  3  strokes,  silent  60 
seconds,  3  strokes,  silent  60  seconds,  etc." 

Light  Buoys  are  used  to  mark  the  entrance  to 
harbors,  to  guard  shoals,  and  to  mark  the  main 
channel  of  large  harbors.  They  may  be  fixed  or 
flashing,  and  red  or  white;  all  light  buoys  are  de- 
scribed in  the  light  lists. 

BUOYS 

All  buoys,  together  with  their  location,  are  de- 
scribed in  the  light  and  buoy  list  of  each  district. 
Certain  rules  govern  buoys  which,  if  remembered, 
make  navigation  by  buoys  a  simple  matter. 

The  particular  feature  about  a  buoy  is  its  color. 
All  buoys  of  each  marked  channel  are  numbered 
from  seaward. 

Red  buoys  have  even  numbers  and  must  be  left 
on  the  starboard  hand  when  entering  harbor. 

Black  buoys  have  odd  numbers  and  must  be  left 
on  the  port  hand  when  entering  harbor. 


114    SMALL  BOAT  NAVIGATION 

When  a  channel  has  two  entrances  from  seaward  local 
rules  must  govern.  Thus  on  the  Maine  coast  where  chan- 
nels have  two  sea  entrances  buoys  in  thoroughfares  and 
passages  are  numbered  and  colored  for  entering  from  East- 
ward. 

Buoys  painted  with  red  and  black  horizontal 
stripes  mark  shoals  or  other  dangers,  and  should 
be  given  a  wide  berth.  Channel  buoys  are  fre- 
quently anchored  abreast  of  these  to  mark  the 
channel. 

Buoys  painted  with  white  and  black  vertical 
stripes  are  midchannel  buoys  and  should  be  passed 
close  to. 

Yellow  buoys  mark  quarantine  anchorages. 

White  buoys  mark  anchorages. 

Shapes  of  Btwys.  Buoys  are  shaped  as  fol- 
lows : 

Can,  cylindrical. 

Nun,  a  truncated  cone,  or 

Spar. 

With  the  exception  of  spar  buoys,  all  buoys 
are  made  of  sheet  iron,  with  water  tight  compart- 
ments to  prevent  sinking  in  case  of  damage. 

Where  there  is  more  than  one  channel  in  a  har- 
bor the  different  buoys  are  used  to  mark  different 
channels;  nun  buoys  mark  the  main  channel,  can 
buoys,  the  secondary  channels,  and  spar  buoys, 
minor  channels.  When  there  is  but  one  channel, 
nun  buoys  are  placed  on  the  starboard  side  and 


LIGHT  AND  BUOY  SYSTEM     115 

can  buoys  on  the  port  (when  entering  from  sea- 
ward). 

Buoys  that  mark  important  shoals  on  the  coast 
are  marked  with  letters  or  numbers ;  {hus  the  buoy 
that  marks  the  Frying  Pan  Shoal  has  F,P. 
painted  on  it. 

Bell  buoys,  whistling  buoys,  and  buoys  with 
balls,  baskets,  and  other  shapes  mounted  on  a 
perch,  mark  turning  points  in  the  channel.  The 
color  and  number  of  the  buoy  indicates  on  which 
side  to  pass.  Where  there  is  much  ice,  bell  and 
gas  buoys  are  frequently  removed  in  winter,  leav- 
ing only  the  spar  buoy  marking  the  position. 

FOG  SIGNALS 

Fog  Signals  are  established  at  all  important 

lighthouses  and  light  vessels  to  aid  navigation  in 

a  fog.     Each  lighthouse  and  light  vessel  has  a 

distinguishing  signal  so  that  it  can  be  identified, 

and  full  descriptions  of  these  are  given  in  the  light 

lists.     The  signal  may  be  given  on  the  whistle  or 

beU. 

CHART  NOMENCLATURE 

Lights  are  indicated  on  some  charts  by  a  yellow 
spot  surrounding  a  black  dot  in  the  case  of  a  white 
light,  and  a  red  dot  in  the  case  of  a  red  light. 
Its  characteristics,  color,  and  range  of  visibility 
are  marked  on  the  chart  abreast  of  it. 


ii6    SMALL  BOAT  NAVIGATION 

Buoys  are  marked  on  the  chart  with  their  num- 
bers and  the  following  abbreviations  to  indicate 
their  characteristics: 

B  —  black. 

R  — red. 

H.S. —  black  and  red,  horizontal  stripeB. 

V.S. —  black  and  white,  vertical  stripes. 

C  —  can. 

N  —  nun. 

S  —  spar. 

The  Character  of  the  Sea  Bottom  is  indicated 
as  follows :  one  letter  abbreviations  are  used  to  in- 
dicate kind  of  bottom,  two  letters  to  indicate  color 
of  bottom,  and  three  letters  for  other  qualifica- 
tions, as  follows: 

M  —  mud.       Yl  —  yellow.        Brk  —  broken. 
G  —  gravel.     Gy  —  gray.         Sml  —  small. 

Soundings  are  indicated  in  fathoms  unless  oth- 
erwise noted.  On  harbor  charts  (^io>ooo  scale) 
sounding  will  probably  soon  be  changed  to  feet. 
Thus,  50  on  the  chart  means  50  fathoms  at  mean 

0 
low  water,     —  means,  *'no  bottom  at  50  fath- 
oms." 50 

MiscelUmeous  Maries,  Other  common  indica- 
tions on  a  chart  are: 


LIGHT  AND  BUOY  SYSTEM    117 

Rock  awash  at  low  water 

Rock,  sunken 

Danger    of    doubtful    existence    (marked 

abreast)     E.D. 

Danger    of    doubtful    position    (marked 

abreast)    P.D. 

Anchorage,  large  vessels ^tJ 

Anchorage,  small  vessels "T* 

Wreck Xf^  or -ffl- 

Lightship     ibI  ■■■» 

Currents  are  marked  by  an  arrow,  with  two 
barbs  for  flood,  and  one  barb  for  ebb ;  the  number 
on  the  arrow  indicates  the  strength  in  knots.  If 
the  current  is  tidal,  one,  two,  or  three  cross  bars 
indicate  the  1st,  2d,  or  3d  quarter  of  the  flow. 
Thus  si^^\  m  indicates  flood  current  in  the  1st 
quarter,  strength  3  knots  per  hour.  Likewise 
5»iL(^  indicates  ebb  current  in  the  3d  quarter, 
strength  5  knots. 


CHAPTER  VII 

WEATHER 
WINDS 

CAUSES  of  Winds.  Wind  is  air  In  hori- 
zontal motion.  It  is  defined  by  its  direc- 
tion and  force.  The  direction  of  the 
wind  is  the  point  of  the  compass  from  which  it 
proceeds.  Its  force  is  generally  measured  by  the 
Beaufort  Scale  described  in  Chapter  II  and  de- 
pends upon  its  velocity.  If  air  is  warmer  in  one 
place  than  in  an  adjacent  place,  the  warm  air  will 
rise  and  will  be  replaced  by  air  flowing  in  from  the 
second  place.  This  creates  a  wind  from  the  sec- 
ond to  the  first  place.  To  take  another  view  of 
the  matter,  in  the  warmer  place  the  barometric 
pressure  is  lower  than  in  the  second  (cooler)  local- 
ity where  the  air  is  descending. 

The  direction  of  winds  is  always  from  a  place  of 
high  barometer  to  one  of  lower  pressure.  The 
Weather  Bureau  supplies  data  from  which  daily 
weather  charts  are  plotted,  showing  the  distribu- 
tion of  barometric  pressures  over  the  United 
States   and  its   adjacent  waters.     These   charts 

2i8 


WEATHER  119 

can  be  consulted  in  any  large  seaport.  Weather 
predictions  made  from  these  charts  are  invaluable 
to  the  mariner. 

The  greater  the  barometric  range' between  two 
adjacent  places,  the  more  violent  the  disturbance 
accompanying  the  transfer  of  air  from  the  region 
of  high  barometer  (called  a  "high")  to  the  re- 
gion of  lower  pressure  (called  a  "low").  When 
suflSciently  violent  we  have  a  gale  or  storm. 

Ascending  currents  of  warm  air  carry  moisture 
that  has  evaporated  from  the  sea.  As  the  air  as- 
cends it  encounters  lower  temperatures  which  con- 
dense the  moisture.  If  this  moist  air  ascends  to 
a  sufficient  height,  or  having  ascended  moves  to  a 
colder  region,  the  moisture  in  the  air  is  suffi- 
ciently cooled  to  be  precipitated  and  we  have  the 
phenomenon  of  rain. 

Land  and  Sea  Breezes.  Generally  speaking, 
the  land  is  warmer  than  the  adjacent  sea  by  day, 
and  cooler  at  night.  This  is  due  to  the  fact  that 
the  land  as  a  whole  absorbs  and  radiates  heat  more 
rapidly  than  will  a  large  body  of  water;  this  is 
especially  the  case  in  summer. 

As  a  consequence  of  the  above,  a  variation  of 
pressure  between  the  land  and  sea  is  established, 
which,  though  small,  nevertheless  is  sufficient  to 
affect  the  local  winds.  Under  normal  conditions, 
the  wind  blows  from  the  sea  toward  the  land  dur- 


120    SMALL  BOAT  NAVIGATION 

ing  the  day,  and  from  the  land  toward  the  sea  at 
night. 

Trade  Winds.  In  the  general  terrestrial  dis- 
tribution of  the  atmosphere  the  equator  is  belted 
by  a  region  of  low  pressures.  To  the  North  and 
South  of  this  belt  are  other  belts  of  high  pressure 
along  the  latitudes  of  approximately  30°  North 
and  South.  Consequently,  winds  blow  rather  con- 
stantly toward  the  equator  over  a  considerable 
area.  Due  to  the  effect  of  the  earth's  rotation 
these  winds  are  from  the  Northeast  in  the  North- 
em  hemisphere  and  from  the  Southeast  in  the 
Southern  hemisphere.  These  prevailing  winds  in 
the  low  latitudes  are  called  the  trades. 

The  Doldrums.  In  the  equatorial  belt  of  low 
pressures  there  is  little  horizontal  motion  to  the 
atmosphere.  The  atmosphere  is  slowly  rising  and 
the  winds  are  stagnant,  blowing  fitfully  in  light 
airs  from  first  one  and  then  another  point  of  the 
compass.  Due  to  the  constant  evaporation  and 
ascending  air  currents  the  weather  is  generally 
cloudy,  with  frequent  thunder  storms.  This  re- 
gion is  called  the  Doldrums, 

The  Horse  Latitudes.  The  belt  of  high  ba- 
rometric pressures  that  lies  along  latitudes  in  the 
Thirties,  North  and  South,  is  another  region  of 
comparative  calms.  Here  the  breezes  are  also 
light,  but  the  weather  is  clear  in  contrast  with  that 


WEATHER  121 

of  the  doldrums.  The  reason  lies  in  the  fact  that 
over  this  region  a  downward  current  of  air  pre- 
vails.    This  region  is  called  the  Horse  Latitudes: 

BAD  WEATHER 

Bad  Weathee  is  a  comparative  term.  A  heavy 
squall  that  would  be  considered  bad  for  a  very 
small  boat  would  not  inconvenience  a  large  vessel. 
For  this  reason  an  attempt  has  been  made  to 
classify  bad  weather  in  an  unscientific  manner 
that  will  be  intelligible  to  the  lay  mind. 

No  amount  of  rain  or  snow  would  endanger  the 
safety  of  even  a  small  boat.  The  factor  in 
weather  that  must  be  considered  is  Wind,  Al- 
though inconvenient  and  uncomfortable,  rain  will 
not  affect  the  placidity  of  the  sea;  the  condition 
of  the  sea  depends  upon  the  strength  of  the  wind, 
and  the  safety  of  a  vessel  depends  upon  the 
strength  and  direction  of  the  wind  and  the  state  of 
the  sea. 

For  the  benefit  of  navigators  of  boats  and  small 
Tessels,  bad  weather  might  be  classified  as  follows : 
(1)  squalls;  (2)  gales;  and  (3)  storms.  This 
classification  depends  upon  the  strength  and  dura- 
tion of  the  bad  weather.  Squalls  are  of  short 
duration,  the  wind  is  variable  and  a  good  sailor  is 
safe  in  almost  any  small  boat.  Gales  are  of 
longer  duration,  the  wind  is  stronger  and  steadier. 


122    SMALL  BOAT  NAVIGATION 

and  the  seas  are  higher.  Storms  are  often  of  sev- 
eral days'  duration,  the  wind  follows  certain  laws, 
being  of  cyclonic  origin,  and  the  seas  become  so 
high  as  to  be  dangerous  to  any  but  good  sized  ves- 
sels. 

Squalls  may  be  encountered  in  almost  any  lo- 
cality. At  some  seasons  they  are  of  daily  occur- 
rence in  the  tropics.  There  is  little  previous 
warning  before  a  squall  breaks,  although  a  long 
period  of  squally  weather  will  generally  be  pre- 
ceded by  a  falling  barometer.  A  squall  may  or 
may  not  be  accompanied  by  rain.  When  accom- 
panied by  rain  the  warning  comes  as  a  grayish 
vertical  curtain  (the  rain)  obscuring  part  of  the 
horizon.  When  this  curtain  is  to  windward  the 
squall  will  probably  strike  the  observer.  When  to 
leeward  it  may  or  may  not  be  encountered.  Often 
squalls  work  to  windward.  If  a  squall  does  not 
contain  rain,  the  first  indication  is  local  agitation 
of  the  surface  of  the  water.  Wind  on  the  water 
can  be  seen  for  a  considerable  distance.  Squalls 
are  accompanied  by  capricious  shifts  of  wind  of 
a  puffy  nature.  The  wind  speed  will  rarely  ex- 
ceed 35  miles  an  hour. 

Handling  the  Boat,  Very  small  boats  under 
sail  should  get  the  sail  off  before  the  squall  strikes, 
as  the  uncertainty  of  the  wind  shifts  might  embar- 
rass.    Any  well  handled  boat  is  safe  in  a  squall. 


WEATHER  123 

If  the  sea  becomes  so  high  as  to  be  uncomfortable 
on  the  course  steered,  run  with  the  sea  astern. 
If  there  is  danger  of  the  sea  breaking  over  the 
stem,  round  to  and  lay  head  to  the  sea.  The  head 
may  be  kept  up  to  the  sea  by  putting  a  drag  over 
the  bow.  A  drag  may  be  made  by  lashing  to- 
gether a  few  oars,  a  spar  and  sail,  or  anything 
that  will  lie  on  or  near  the  surface. 

Gales  may  be  encountered  in  almost  every  local- 
ity. In  our  own  waters  they  may  be  found  in  the 
Gulf  of  Mexico,  along  the  entire  Atlantic  and  Pa- 
cific sea  coasts,  and  in  the  Atlantic  along  paths 
North  of  30°  Lat.  and  South  of  25°  Lat.  The  ba- 
rometer gives  early  indications  of  a  gale.  A  stead- 
ily falling  barometer,  accompanied  by  a  steadily 
increasing  wind  indicates  the  approach  of  a  gale. 
A  dull  lowering  sky.  Nimbus  clouds  or  "  scud,"  with 
Alto-stratus  or  Cirro-stratus  above,  and  a  rising 
sea,  all  precede  a  gale.  A  red  sky  in  the  morning 
and  halos  around  the  moon  or  sun  may  be  early 
indications.  Gales  are  generally  accompanied  by 
rain,  hail,  sleet,  or  snow.  The  wind  varies  from 
40  to  60  miles  per  hour.  As  the  wind  increases 
in  intensity  the  barometer  falls  rapidly.  These 
two  conditions  taken  together  are  almost  certain 
signs  of  a  gale. 

Handling  the  Boat.  Small  boats  should  seek 
ihelter.     Sail  should  be  doused  on  sailing  craft. 


124    SMALL  BOAT  NAVIGATION 

Small  craft  will  do  well  to  run  with  the  sea  aft, 
with  just  enough  speed  on  to  keep  the  sea  from 
breaking  over  the  stem.  If  for  any  reason  it  is 
impossible  to  run  this  way  and  it  becomes  neces- 
sary to  lay  to,  do  so  with  the  sea  ahead,  with  a 
good  drag  over  the  bow.  If  necessary  to  lie  hove 
to  in  fair  sized  craft  it  may  be  found  that  the  ves- 
sel is  more  comfortable  if  hove  to  stern  to  the  sea 
without  a  drag.  Large  vessels  can  generally  pur- 
sue their  course  through  a  gale,  but  the  speed 
should  be  reduced  as  the  gale  strengthens. 

Storms  are  invariably  of  cyclonic  origin  and 
follow  well  established  rules  in  their  movements 
and  wind  shifts.  It  is  beyond  the  scope  of  this 
work  to  discuss  the  whole  subject,  but  a  few  indi- 
cations of  their  approach  and  rules  for  handling 
vessels  in  a  storm  will  be  given.  The  duration  of 
a  storm  may  be  several  days,  and  during  this  en- 
tire period  the  wind  blows  at  75  miles  per  hour  or 
more.  It  gradually  shifts  in  direction  according 
to  well  established  rules  given  hereafter.  Indica- 
tions of  its  approach  are  available  for  at  least  24 
hours  before  the  storm  breaks  in  all  its  fury. 

Early  Indications.  A  storm  is  preceded  by  an 
abnormal  rise  of  the  barometer,  with  cool,  dry, 
fresh  winds  and  a  cessation  or  reversal  of  the  ordi- 
nary land  and  sea  breezes.  The  atmosphere  be- 
comes very  transparent.     A  long  low  swell  is  pres- 


WEATHER  125 

ent  at  a  great  distance  from  the  storm  center, 
sometimes  several  hundred  miles,  and  this  is 
occasionally  accompanied  by  hurricane  rollers. 
When  there  is  no  intervening  island  or  land  to  di- 
vert them,  the  direction  of  the  rollers  indicates 
the  direction  of  the  storm  center.  Feathery  Cir- 
rus clouds  form  on  the  horizon  and  radiate  from  a 
point  on  the  horizon,  which  point  also  indicates 
the  direction  of  the  storm  center. 

Unmistakable  Signs,  As  the  storm  develops 
and  comes  nearer  the  sky  becomes  hazy  and  is  cov- 
ered by  a  veil  of  Cirrus  clouds  which  form  halos 
by  day  and  night.  The  barometer  falls  very  rap- 
idly and  becomes  unsteady.  The  air  is  heavy,  hot, 
and  moist  and  the  sky  assumes  red  and  violet  tints 
at  dawn  and  sunset.  A  low  solid  hurricane  cloud 
bank  forms  on  the  horizon  having  the  appearance 
of  land.  Squalls  break  off  and  diverge  from  this 
cloud  bank  and  later  these  squalls  pass  the  line  of 
center  of  the  bank.  Fine  misty  rain  forms  with 
a  heavy  cross  sea.  As  the  storm  develops  the 
wind  rises  and  the  barometer  falls  more  rapidly 
and  becomes  more  unsteady.  The  wind  blows  at 
more  than  90  miles  per  hour. 

Location  of  Storm  Center,  During  the  early 
observations  the  location  of  the  storm  center  can 
be  found  by  the  directions  of  the  rollers  or  of  the 
storm  bank  as  given  above.     As  the  storm  devel- 


126    SMALL  BOAT  NAVIGATION 

Ops  and  these  can  no  longer  be  observed,  the  direc- 
tion of  the  center  can  be  taken  as  10  to  12  compass 
points  from  the  direction  of  the  wind,  to  the  right 
m  the  Northern  hemisphere  and  to  the  left  in  the 
Southern  hemisphere.  As  the  storm  increases  in 
intensity  and  the  center  approaches,  after  the 
barometer  has  fallen  as  much  as  one-half  inch,  the 
direction  of  the  center  may  be  taken  at  8  points 
from  the  direction  of  the  wind. 

Wind  Shifts,  In  the  Northern  hemisphere  the 
wind  rotates  around  the  storm  center  in  an  anti- 
clockwise direction.  To  an  observer  on  a  vessel 
if  the  wind  appears  to  shift  to  the  right,  the  ves- 
sel is  in  the  dangerous  zone  of  the  storm;  if  the 
wind  appears  to  shift  to  the  left  the  vessel  is  in 
the  navigable  zone ;  if  the  wind  blows  steadily  from 
one  direction  as  it  increases  in  intensity,  the  vessel 
is  in  the  path  of  the  storm  center. 

Handling  the  Boat,  Small  craft  must  seek 
shelter  on  the  approach  of  a  storm.  Only  large 
vessels  are  safe  in  them.  There  is  apparently  no 
limit  to  the  degree  of  intensity  of  the  wind,  and  the 
seas  become  very  high  and  irregular.  If  forced 
to  lie  to  this  may  be  done  with  a  drag,  but  a  safer 
way  is  to  run  before  the  storm  at  just  sufficient 
speed  to  keep  the  seas  from  breaking  over  the 
quarter.  The  following  table  shows  the  maneu- 
vers for  sailing  vessels  caught  in  a  storm: 


WEATHER 


127 


IN    THE    NORTHERN    HEMISPHERE 


Heavb  to  oh  the 

Starboabd  Tack  to 

Observe  the  Wiotj 

Wind 

Zone 

If  the   wind  hauls 

The    vessel    is    in 

Rim    close    hauled 

to   the   right 

the  right  or  dan- 

on  the  starboard 

geroiis   zone 

tack 
If  obliged  to  lie  to 
do     so     on     the 
starboard  tack. 

If  the  wind  hauls 

The     vessel    is    in 

Run  with  the  wind 

to  the  left 

the  left  or  nav- 

on      the       star- 

igable  zone 

board  quarter 
If    obliged    to    lie 
to  do  so  on  the 
port  tack 

If    the    wind     re- 

The    vessel     is    in 

Get    the    wind    on 

mains  steadj 

the  path   of  the 

the      starboard 

storm   center 

quarter  and  keep 
that      compass 
course 
If    obliged    to    lie 
to  do  so  on  tack 
that     the     wind 
and  sea  will  draw 
aft 

Large,  full  powered  vessels  will  do  well  in  the 
dangerous  zone  to  run  with  the  wind  ahead  or  on 
the  starboard  bow  as  long  as  possible.  This  will 
work  the  vessel  away  from  the  storm  center.  The 
speed  must  be  reduced,  in  fact  just  make  steerage 
way.  When  it  is  no  longer  practicable  to  run 
into  the  seas  lie  to  or  run  with  the  wind  on  the 


128    SMALL  BOAT  NAVIGATION 

starboard  quarter  with  just  sufficient  speed  to 
keep  the  seas  from  breaking  aboard. 

When  in  the  left  or  navigable  zone,  run  with  the 
wind  on  the  starboard  quarter  at  a  reduced  speed. 
Lie  to  when  necessary.  If  the  vessel  is  in  the 
track  of  the  storm  center  get  the  wind  on  the  star- 
board quarter,  note  the  compass  course,  and  keep 
this  course  until  the  vessel  has  worked  its  way  out 
of  the  storm. 

Tornadoes  and  Water  Spouts.  A  tornado 
might  be  likened  to  a  concentrated  storm,  al- 
though this  would  not  be  technically  correct.  It 
depends  upon  an  unstable  and  very  humid  state  of 
the  atmosphere,  and  is  cyclonic  in  nature.  A  tor- 
nado may  only  be  a  few  hundred  yards  in  diame- 
ter. During  an  unstable  and  very  humid  state  of 
the  atmosphere,  a  warm,  moist  air  current, 
stronger  than  usual  forces  its  way  up,  and  once 
started,  increases  in  violence. 

The  upward  velocity  and  velocity  of  gyration 
are  extremely  high,  the  former  reaching  as  much 
as  150  miles  per  hour,  and  the  latter  as  much  as 
SOO  miles  per  hour.  As  the  diameter  is  very  small 
the  vortex  is  very  steep,  and  the  barometer  may 
fall  from  the  normal  to  nearly  zero,  a  state  of  per- 
fect vacuum.  This  accounts  for  the  great  dam- 
age done  by  this  class  of  storm,  the  inside  pressure 
of  a  building  being  normal  and  the  outside  pres- 


WEATHER  129 

sure  being  nearly  zero,  the  tendency  is  for  the 
building  to  burst.  This  class  of  storm,  due  to  its 
causes  of  formation,  is  always  accompanied  by 
rain  around  its  outside.  There  is  no  rain  in  its 
center,  the  upward  tendency  of  the  atmosphere 
preventing  the  moisture  from  descending. 

A  Water  Spout  is  simply  a  tornado  formed  at 
sea  in  atmosphere  laden  with  moisture  where  the 
dew  point  stratum  is  comparatively  near  the 
earth's  surface.  It  is  an  erroneous  belief  that  the 
water  column  is  formed  by  water  sucked  up  from 
the  sea.  This  is  not  a  fact.  The  water  column  is 
due  to  moisture  drawn  down  from  the  heavy  mois- 
ture-laden atmosphere.  It  is  doubtful  whether 
water  is  drawn  up  from  the  sea  to  any  great  ex- 
tent, and  it  is  certain  that  the  sea  surface  is  not 
drawn  up  more  than  30  feet,  the  height  of  the 
water  barometer. 


CHAPTER  Vni 

RULES    OF    THE    KOAD 

SHIPPING,  both  on  the  high  seas  and  in 
pilot  waters,  is  bound  by  certain  rules  as 
to  the  lights  to  be  carried,  navigational 
signals  to  be  made,  and  the  manner  in  which  to 
maneuver  to  avoid  collision. 

International  Rules  of  the  Road  govern  these 
matters  on  the  high  seas  and  they  are  enforced  by 
Maritime  Law.  They  are  agreed  to  by  the  prin- 
cipal nations  and  are  promulgated  by  the  legisla- 
tive bodies  thereof.  These  rules  always  apply 
when  on  the  high  seas  or  in  waters  not  under  the 
territorial  jurisdiction  of  any  particular  nation. 

Inland  Rules  of  the  Road.  Rules  for  the  con- 
duct of  vessels  in  the  territorial  waters  of  differ- 
ent countries  are  promulgated  by  the  legislative 
bodies  thereof.  Those  promulgated  by  the  U.  S. 
Congress  are  similar  in  many  respects  to  the  Inter- 
national Rules.  Important  differences  therein 
are  pointed  out  in  this  chapter.  These  rules  are 
not  applicable  to  vessels  on  the  Great  Lakes,  where 
a  special  set  of  rules  govern. 

I3D 


X3X 


132    SMALL  BOAT  NAVIGATION 

These  rules  apply  to  all  vessels  plying  the  in- 
land waters  of  the  United  States ;  the  limits  of 
these  waters  are  shown  in  Figure  22.  All  waters 
inside  the  dotted  lines  shown  in  this  Figure  are 
considered  U.  S.  Inland  waters  for  navigation. 
The  rules  are  too  voluminous  to  quote  vn  toto  so 
a  summary  of  the  important  ones  follows: 

INLAND  RULES  OF  THE  ROAD 

Classification  of  Vessel.  Any  vessel  pro- 
pelled fez/  machinery  is  classed  as  a  steamer. 
Steamers  when  under  sail  and  not  under  steam  are 
classed  as  sailing  vessels.  In  this  case  they  must 
carry,  by  day,  a  black  ball  or  shape  forward  to 
distinguish  them  from  steamers  under  way. 

A  vessel  is  considered  underway  when  she  is  not 
at  anchor,  or  made  fast  to  the  shore  or  aground. 

Lights  of  Vessels.  All  lights  that  are  re- 
quired by  the  rules  of  the  road  must  he  shown  from 
sumset  to  su/nrise,  in  all  weathers,  and  during  such 
time  no  other  lights  that  may  be  mistaken  for  the 
prescribed  lights  shall  be  exhibited. 

1.  Steamier  Lights  When  Underway,  (a) 
Forward,  a  white  light,  visible  at  least  5  miles 
over  an  arc  of  20  points  of  the  horizon,  from  ahead 
to  2  points  abaft  both  beams.  This  is  known  as 
the  masthead  light, 

(b)     On  the  starboard  side,  a  green  light,  visi- 


RULES  OF  THE  ROAD       133 

ble  at  least  2  miles  over  an  arc  of  10  points,  from 
ahead  to  2  points  abaft  the  starboard  beam. 
This  is  known  as  the  starboard  side  light, 

(c)  On  the  port  side,  a  red  light,  visible  at 
least  2  miles  over  an  arc  of  10  points,  from  ahead 
to  2  points  abaft  the  port  beam.  This  is  known 
as  the  port  side  light, 

(d)  An  additional  light  similar  to  that  de- 
scribed in  (a)  shall  be  carried  aft  and  higher  than 
(a).  This  additional  light  forms,  with  the  mast- 
head light,  range  lights. 

(e)  The  green  and  red  lights  must  have  in- 
board screens  so  placed  as  to  prevent  them  show- 
ing across  the  bow.  These  lights  are  carried 
lower  than  the  masthead  light. 

The  additional  light  described  in  (d),  which 
with  the  masthead  light  forms  a  range,  is  compul- 
sory in  Inland  Waters,  except  in  the  case  of  sea- 
going vessels  and  ferry  boats.  The  International 
Rules  make  this  light  optional  outside  Inland  Wa- 
ters. 

It  is  apparent  that  when  a  vessel  on  an  even 
keel,  carrying  range  lights,  is  seen  head  on,  the 
lights  are  seen  one  above  the  other;  if  the  vessel 
changes  course  the  lights  will  open  out,  the  lower 
one  away  from  the  upper  one  in  the  direction  to 
which  the  vessel's  head  is  changing.  Such  change 
gives  instant  notice  of  change  of  course  and  is 


134    SMALL  BOAT  NAVIGATION 

more  reliable  than  side  lights  because  the  distance 
at  which  the  range  lights  can  be  seen  is  so  much 
greater. 

Care  should  be  exercised  not  to  confuse  range 
lights  with  towing  lights,  given  under  2  (a). 

2.  Special  Steajmee  Lights,  (a)  When  tow- 
ing, a  steamer  carries  its  regular  lights  and  an 
additional  light  similar  to  the  masthead  light  in  a 
vertical  line  therewith,  and,  if  towing  more  than 
one  vessel  and  the  tow  exceeds  600  feet,  it  carries 
two  such  additional  lights.  These  lights  must  be 
carried  at  least  3  feet  apart. 

International  Rules  require  that  outside  of  in- 
land waters  towing  lights  must  be  at  least  6  feet 
apart.  Care  must  be  taken  not  to  confuse  towing 
lights  with  range  lights.  When  range  lights  and 
towing  lights  are  both  carried,  four  lights  in  a 
vertical  line  may  be  seen.  At  distances  beyond 
four  miles  2  lights  6  feet  apart  blend  into  one. 

(b)  Pilot  Vessels  when  on  their  station  shall 
carry  forward  a  white  light  visible  all  round  the 
horizon  and  shall  exhibit  a  flare-up  light  at  short 
intervals  not  to  exceed  15  minutes. 

On  the  near  approach  to  or  of  other  vessels  they 

shall  flash  their  side  lights  at  short  intervals  to 

indicate  their  heading. 

In  addition  to  the  above  special  lights  required  by  the 
Inland  Rules,  the  International  Rules  require  the  follow- 
ing lights,  outside  inland  waters: 


RULES  OF  THE  ROAD       135 

(c)  A  Vessel  Not  Under  Command  carries  for- 
ward two  red  lights  in  a  vertical  line  one  over 
the  other,  visible  all  round  the  horizon  at  least  2 
miles.  In  the  daytime  it  carries  two  black  balls  or 
shapes. 

(d)  A  Vessel  Engaged  in  Laying  or  Picking 
Up  a  Cable  carries  forward  three  lights  in 
a  vertical  line.  The  highest  and  lowest  lights  are 
red  and  the  middle  light  is  white.  All  are  visible 
all  round  the  horizon  at  least  2  miles. 

(e)  When  making  way  through  the  water 
Towing  Steamers,  Cable  Vessels,  and  Vessels  Not 
Under  Command  must  carry  side  lights  as  pre- 
scribed for  steamers. 

3.  Sailing  Vessel  Lights.  A  sailing  vessel  or 
a  vessel  being  towed  must  carry  the  side  lights  pre- 
scribed for  steamers  but  must  not  carry  a  mast- 
head light. 

4.  Small  Steamers,  Sail  Vessels,  and  Row 
Boats,  (a)  Steam  vessels  of  less  than  J^O  tons 
carry  a  masthead  light  visible  2  miles  and  side 
lights  visible  1  mile,  but  in  lieu  of  side  lights  m>ay 
carry  a  combined  lantern  showing  a  green  and  red 
light  from  right  ahead  to  9.  points  abaft  the  beam 
on  their  respective  sides.  This  lantern  is  carried 
at  least  3  feet  below  the  masthead  light. 

(b)  Rowing  Boats,  whether  under  oars  or  sail, 
shall  have  ready  at  hand  a  white  lantern  which 


136    SMALL  BOAT  NAVIGATION 

shall  be  temporarily  exhibited  in  time  to  prevent 
collision. 

5.  Lights  for  an  Overtaken  Vessel.  A  ves- 
sel which  is  being  overtaken  shall  show  from  her 
stern  a  white  light  or  flare  up  light  to  the  over- 
taking vessel. 

6.  Anchor  Lights.^  (a)  A  vessel  under  150 
feet  in  length  shall  carry  forward  at  a  height  not 
over  20  feet  a  white  light  visible  all  round  the  hori- 
zon at  least  1  mile. 

(b)  A  vessel  of  150  feet  or  over  shall  carry 
forward  at  a  height  between  20  and  40  feet  a  white 
light  visible  all  round  at  least  1  mile.  At  the 
stem  she  shall  carry  a  similar  light  at  least  15 
feet  lower  than  the  forward  light. 

In  addition  to  the  above  the  International  rules 
prescribe : 

(c)  A  Vessel  Agrownd  in  or  near  a  fairway 
shall  carry  anchor  lights  as  above  and  in  addition 
the  two  red  lights  prescribed  in  2  (c).  No  pro- 
vision is  made  for  vessels  aground  in  the  Inland 
Rules  and  they  carry  the  regular  anchor  lights. 

7.  Lights  for  Ferry  Boats  are  prescribed  by 
special  rules  established  by  the  Supervising  In- 
spector General  of  Steam  Vessels  and  approved  by 
the  Secretary  of  Commerce. 

iNo  distinction  is  made  between  steamers  and  sailing 
vessels  in  anchor  lights. 


RULES  OF  THE  ROAD       137 

8.  Rafts  and  Other  Watee  Ceaft  not  specif- 
ically provided  for,  navigating  by  hand  power, 
horse  power,  or  by  the  current  of  £^  river  shall 
carry  one  or  more  good  white  lights  in  such  man- 
ner as  is  provided  by  the  Board  of  Supervising 
Inspectors  of  Steam  Vessels. 

SOUND  SIGNALS 

Sound  Signals  foe  Passing  Steamees.  A 
Short  Blast  is  one  of  about  one  second  duration. 

When  steamers  are  in  sight  of  one  another 
change  of  course  is  indicated  by  the  following  sig- 
nals: 

(a)  One  short  blast  means  "I  am  directing 
my  course  to  starboard." 

(b)  Two  short  blasts  means  "  I  am  directing 
my  course  to  port." 

(c)  Three  short  blasts  means  "  My  engines 
are  going  full  speed  astern." 

Sound  Signals  foe  Fog.  Fog  signals  ar« 
given  by  steamers  on  the  whistle  or  siren. 

Fog  signals  are  given  by  sailing  vessels  and  ves-» 
sels  being  towed  on  the  fog  horn. 

A  Prolonged  Blast  means  one  of  4  to  6  minutes' 
duration. 

1.  Fog  signals  must  always  be  made  by  all  vesi 
sels  in  fog,  mist,  falling  snow,  or  heavy  rain 
storm,  whether  by  day  or  night. 


138    SMALL  BOAT  NAVIGATION 

2.  Steam  Vessels  Underway,  A  steam  vessel 
underway  shall  sound  at  intervals  of  not  more 
than  one  minute,  a  prolonged  blast. 

The  International  Rules  differ  materially  from 
the  above  and  are  quoted  here  for  use  on  the  high 
seas: 

(a)  A  steam  vessel  having  way  upon  her  shall 
sound,  at  intervals  of  not  more  than  2  minutes,  a 
prolonged  blast. 

(b)  A  steam  vessel  underway,  hut  stopped^ 
and  having  no  way  upon  her,  shall  sound  at  in- 
tervals of  not  more  than  2  minutes,  two  prolonged 
blasts,  with  an  interval  of  about  one  second  be- 
tween. 

The  navigator  must  hold  clearly  in  his  mind  the 
fact  that  the  "  sound  signals  in  a  fog  "  must  be 
used  at  all  times  in  inclement  weather,  up  to  the 
moment  of  sighting  another  vessel.  When  two 
vessels  come  in  sight  of  each  other  then  "  sound 
signals  for  passing  vessels  "  should  be  used.  It  is 
a  common  error  among  seamen  to  use  passing  sig- 
nals when  two  vessels  are  within  sound  hut  not 
sight  of  each  other.  This  practice  cannot  be  too 
severely  condemned. 

3.  Sailing  Vessels  Underway  shall  sound  at  in- 
tervals of  not  more  than  1  minute,  when  on  the 
starboard  tack,  one  blast ;  when  on  the  port  tack, 


RULES  OF  THE  ROAD       139 

two  blasts;  when  with  the  wind  abaft  the  beam, 
three  blasts  in  succession. 

4.  Vessels  at  Anchor  shall,  at  intervals  of  not 
more  than  one  minute,  ring  the  bell  rapidly  for 
about  6  seconds. 

6.  A  Vessel  When  Towing  or  being  towed  shall 
sound  at  intervals  of  not  more  than  2  minutes, 
three  blasts  in  succession,  namely:  One  pro- 
longed blast  followed  by  two  short  ones. 

The  International  Rules  prescribe  this  same 
signal  for  vessels  employed  in  laying  or  picking  up 
a  cable  and  for  vessels  underway  but  not  under 
command. 

6.  Rafts  and  other  small  craft  not  specifically 
provided  for  navigating  by  hand  power,  horse 
power,  or  by  the  current  of  a  river,  shall  sound  a 
blast  of  the  fog  horn  or  equivalent  signal,  at  in- 
tervals of  not  more  than  one  minute. 

SPEED  IN  A  FOG 

Every  vessel  shall,  in  a  fog,  mist,  falling  snow, 
or  heavy  rain  storms,  go  at  a  moderate  speed,  hav- 
ing careful  regard  to  the  existing  circumstances 
and  conditions. 

A  steam  vessel  hearing,  apparently  forward  of 
her  beam,  the  fog  signal  of  a  vessel  the  position  of 
which  is  not  ascertained  shall,  so  far  as  the  cir- 


I40    SMALL  BOAT  NAVIGATION 

cumstances  of  the  case  admit,  stop  her  engines, 
and  then  navigate  with  caution  until  danger  of 
collision  is  over. 

What  constitutes  moderate  speed  in  a  fog  is  a 
much  mooted  question.  However,  it  can  be  de- 
fined as  such  speed  as  will  with  certainty  prevent 
collision.  Clearly  speed  that  might  be  permissi- 
ble on  the  high  seas  would  be  too  high  for  crowded 
inland  waters.  It  might  even  be  necessary  to 
stop  and  anchor  in  some  cases. 

STEERING  AND   SAILING  RULES 

1.  Preliminary.  Risk  of  collision  can,  when 
circumstances  permit,  be  ascertained  by  carefully 
watching  the  compass  bearing  of  an  approaching 
vessel.  //  the  hearing  does  not  appreciably 
change^  such  risk  should  be  deemed  to  exist. 

%  Sailing  Vessels.  When  two  sailing  vessels 
are  approaching  each  other,  so  as  to  involve  risk 
of  collision,  one  of  them  will  keep  out  of  the  way 
of  the  other,  as  follows : 

(a)  A  vessel  which  is  running  free  shall  keep 
out  of  the  way  of  a  vessel  which  is  closehauled. 

(b)  A  vessel  which  is  closehauled  on  the  port 
tack  shall  keep  out  of  the  way  of  a  vessel  which  is 
closehauled  on  the  starboard  tack. 

(c)  When  both  are  running  free,  with  the 
wind  on  different  sides,  the  vessel  which  has  the 


RULES  OF  THE  ROAD       141 

wind  on  the  port  side  shall  keep  out  of  the  way  of 
the  other. 

(d)  When  both  are  running  free,  with  the 
wind  on  the  same  side,  the  vessel  which  is  to  wind- 
ward shall  keep  out  of  the  way  of  the  vessel  which 
is  to  leeward. 

(e)  A  vessel  which  has  the  wind  aft  shall  keep 
out  of  the  way  of  the  other  vessel. 

3.  Steam  Vessels.  When  steam  vessels  are 
approaching  each  other  head  and  head,  that  is  end 
on,  or  nearly  so,  it  shall  be  the  duty  of  each  to 
pass  on  the  port  side  of  the  other ;  and  either  ves- 
sel shall  give,  as  a  signal  of  her  intention,  one 
short  and  distinct  blast  of  her  whistle,  which  the 
other  vessel  shall  answer  promptly  by  a  similar 
blast  of  her  whistle,  and  thereupon  such  vessels 
pass  upon  the  port  side  of  each  other.  But  if 
the  courses  of  such  vessels  are  so  far  on  the  star- 
board of  each  other  as  not  to  be  considered  as 
meeting  head  and  head,  either  vessel  shall  imme- 
diately give  two  short  and  distinct  blasts  of  her 
whistle,  which  the  other  vessel  shall  answer 
promptly  by  two  similar  blasts  of  her  whistle,  and 
they  shall  pass  on  the  starboard  side  of  each 
other. 

The  foregoing  only  applies  to  cases  where  ves- 
sels are  meeting  end  on,  or  nearly  end  on,  in  such 
a  manner  as  to  involve  risk  of  collision;  in  other 


142    SMALL  BOAT  NAVIGATION 

words,  to  cases  in  which,  by  day,  each  vessel  sees 
the  masts  of  the  other  in  line,  or  nearly  in  line, 
with  her  own,  and  by  night  to  cases  in  which  each 
vessel  is  in  such  a  position  as  to  see  both  the  side 
lights  of  the  other. 

It  does  not  apply  by  day  to  cases  in  which  a  ves- 
sel sees  another  ahead  crossing  her  own  course, 
or  by  night  to  cases  where  the  red  light  of  one 
vessel  is  opposed  to  the  red  light  of  the  other,  or 
where  the  green  light  of  one  vessel  is  opposed  to 
the  green  light  of  the  other,  or  where  a  red  light 
without  a  green  light  or  a  green  light  without  a 
red  light  is  seen  ahead,  or  where  both  green  and 
red  lights  are  seen  anywhere  but  ahead. 

(b)  If,  when  steam  vessels  are  approaching 
each  other,  either  vessel  fails  to  understand  the 
course  or  intention  of  the  other,  from  any  cause, 
the  vessel  so  in  doubt  shall  immediately  signify  the 
same  by  giving  several  short  and  rapid  blasts,  not 
less  than  four,  of  the  steam  whistle.  This  is  com- 
monly known  as  the  danger  signal. 

(c)  Whenever  a  steam  vessel  is  nearing  a 
short  bend  or  curve  in  the  channel,  where,  from  the 
height  of  the  bank  or  other  cause,  a  steam  vessel 
approaching  from  the  opposite  direction  can  not 
be  seen  for  a  distance  of  half  a  mile,  such  steam 
vessel,  when  she  shall  have  arrived  within  half  a 
mile  of  such  curve  or  bend,  shall  give  a  signal  by 


RULES  OF  THE  ROAD       143 

one  long  blast  of  the  steam  whistle,  which  signal 
shall  be  answered  bj  a  similar  blast  given  bj  any 
approaching  steam  vessel  that  may  be  within  hear- 
ing. Should  such  signal  be  so  answered  by  a 
steam  vessel  upon  the  farther  side  of  such  bend, 
then  the  usual  signals  for  meeting  and  passing 
shall  immediately  be  given  and  answered;  but  if 
the  first  alarm  signal  of  such  vessel  be  not  an- 
swered, she  is  to  consider  the  channel  clear,  and 
govern  herself  accordingly. 

When  steam  vessels  are  moved  from  their  docks 
or  berths,  and  other  boats  are  liable  to  pass  from 
any  direction  toward  them,  they  shall  give  the 
same  signal  as  in  the  case  of  vessels  meeting  at  a 
bend,  but  immediately  after  clearing  the  berths  so 
as  to  be  fully  in  sight,  they  shall  be  governed  by 
the  steering  and  sailing  rules. 

(d)  When  steam  vessels  are  running  in  the 
same  direction,  and  the  vessel  which  is  astern  shall 
desire  to  pass  on  the  right  or  starboard  hand  of 
the  vessel  ahead,  she  shall  give  one  short  blast  on 
the  steam  whistle  as  a  signal  of  such  desire;  and 
if  the  vessel  ahead  answers  with  one  blast,  she  shall 
put  her  helm  to  port ;  or  if  she  shall  desire  to  pass 
on  the  left  or  port  side  of  the  vessel  ahead,  she 
shall  give  two  short  blasts  of  the  steam  whistle  as 
a  signal  of  such  desire;  and  if  the  vessel  ahead 
answers  with  two  blasts,  shall  put  her  helm  to  star- 


144    SMALL  BOAT  NAVIGATION 

board;  or  if  the  vessel  ahead  does  not  think  it 
safe  for  the  vessel  astern  to  attempt  to  pass  at 
that  point,  she  shall  immediately  signify  the  same 
by  giving  several  short  and  rapid  blasts  of  the 
steam  whistle,  not  less  than  four,  and  under  no 
circumstances  shall  the  vessel  astern  attempt  to 
pass  the  vessel  ahead  until  such  time  as  they  have 
reached  a  point  where  it  can  be  safely  done,  when 
said  vessel  ahead  shall  signify  her  willingness  by 
blowing  the  proper  signals.  The  vessel  ahead 
shall  in  no  case  attempt  to  cross  the  bow  or  crowd 
upon  the  course  of  the  passing  vessel. 

(e)  The  whistle  signals  provided  in  the  rules 
under  this  article  for  steam  vessels  meeting,  pass- 
ing, or  overtaking  are  never  to  be  used  except 
when  steamers  are  in  sight  of  each  other  and  the 
course  and  position  of  each  can  be  determined  in 
the  daytime  by  a  sight  of  the  vessel  itself  or  by 
night  by  seeing  its  signal  lights.  In  fog,  mist, 
falling  snow,  or  heavy  rain  storms,  when  vessels 
cannot  see  each  other,  fog  signals  only  must  be 
given. 

(f)  When  two  steam  vessels  are  crossing,  so 
as  to  involve  risk  of  collision,  the  vessel  which  has 
the  other  on  her  own  starboard  side  shall  keep 
out  of  the  way  of  the  other. 

(g)  When  a  steam  vessel  and  a  sailing  vessel 
are  proceeding  in  such  directions  as  to  involve  risk 


RULES  OF  THE  ROAD       145 

of  collision,  the  steam  vessel  shall  keep  out  of  the 
way  of  the  sailing  vessel. 

(h)  Where  by  any  of  these  rules,  one  of  the 
two  vessels  is  to  keep  out  of  the  way,  the  other 
shall  keep  her  course  and  speed. 

(i)  Every  vessel  which  is  directed  to  keep  out 
of  the  way  of  another  vessel  shall,  if  the  circum- 
stances of  the  case  permit,  avoid  crossing  ahead  of 
the  other. 

(j)  Every  steam  vessel  which  is  directed  by 
these  rules  to  keep  out  of  the  way  of  another  ves- 
sel shall,  on  approaching  her,  if  necessary,  slacken 
her  speed  or  stop  or  reverse. 

Emphasis  should  be  laid  upon  paragraphs  (h) 
and  (i).  The  law  prescribes  that  when  one  of 
two  vessels  must  keep  out  of  the  way  the  other 
must  keep  her  course  and  speed.  The  vessel  that 
must  keep  out  of  the  way  shall,  if  the  circum- 
stances permit,  avoid  crossing  ahead  of  the  other. 

The  following  rules  are  quoted  from  the  Inter- 
national Rules.     They  apply  in  Inland  Waters : 

1.  Notwithstanding  anything  in  the  rules  every 
vessel,  overtaking  any  other,  shall  keep  out  of  the 
way  of  the  overtaken  vessel.  Every  vessel  com- 
ing up  with  another  vessel  from  any  direction  more 
than  two  points  abaft  her  beam  shall  be  deemed 
an  overtaking  vessel.  In  case  of  doubt,  the  vessel 
is  to  assume  herself  an  overtaking  vesseL 


146    SMALL  BOAT  NAVIGATION 

2.  In  narrow  channels  every  steamer  shall,  when 
it  is  safe  and  practicable,  keep  to  the  side  of  the 
fairway  or  mid-channel  which  lies  on  the  starboard 
side  of  such  vessel. 

Sailing  vessels  underway  shall  keep  out  of  the 
way  of  sailing  vessels  or  boats  fishing  with  lines, 
nets,  or  trawls. 

DISTRESS  SIGNALS 

When  a  vessel  is  in  distress  and  requires  assist- 
ance from  other  vessels  or  from  shore  the  following 
shall  be  the  signals  to  be  used  or  displayed  by  her, 
either  together  or  separately: 

1.  In  the  Daytime  a  continuous  sounding  with 
any  fog  signal  apparatus,  or  firing  a  gun. 

^.  At  Night  (a)  Flames  on  the  vessel  as  from  a 
burning  tar  barrel,  oil  barrel,  and  so  forth. 

(b)  A  continuous  sounding  with  any  fog  sig- 
nal apparatus,  or  firing  a  gun. 

PRUDENCE  AND  PRECAUTION 

1.  In  obeying  and  construing  these  rules  due  re- 
gard shall  be  had  to  all  dangers  of  navigation  and 
collision,  and  to  any  special  circumstances  which 
may  render  a  departure  from  these  rules  necessary 
to  avoid  immediate  danger. 

2.  Nothing  in  the  rules  shall  exonerate  any  ves- 


RULES  OF  THE  ROAD       147 

sel,  or  the  owner  or  master  or  crew  thereof,  from 
the  consequences  of  any  neglect  to  carry  lights  or 
signals,  or  of  any  neglect  to  keep  a  proper  look- 
out, or  of  the  neglect  of  any  precaution  which  may 
be  required  by  the  ordinary  practice  of  seamen,  or 
by  the  special  circumstances  of  the  case. 

PENALTIES 

"Penalties  are  prescribed  for  the  infringement 
of  these  rules  by  all  nations  that  have  adopted 
them  as  laws,  and  these  penalties  do  not  depend 
upon  the  question  whether  damage  has  or  has  not 
resulted  from  the  infringement. 

"  Where  damage  is  done,  and  can  be  shown  to  be 
the  result  of  neglect  or  violation  of  the  rules,  it  is 
held,  in  the  absence  of  proof  to  the  contrary,  to 
be  the  fault  of  the  person  having  charge  of  the 
deck  of  the  vessel  offending,  who  will  be  considered 
guilty  of  a  misdemeanor  and  punishable  therefor. 
If  death  ensues,  he  will  be  subject  to  a  charge  of 
manslaughter. 

**  In  every  case  of  collision,  it  is  the  duty  of  the 
person  in  charge  of  each  vessel  to  stay  by  the 
other  and  render  such  assistance  as  may  be  prac- 
ticable, provided  he  can  do  so  without  damage  to 
his  own  ship,  passengers,  or  crew. 

**  He  is  also  required  to  give  to  the  master  of  the 


148    SMALL  BOAT  NAVIGATION 

other  ship  the  name  of  his  own  ship  and  of  the 
port  to  which  she  belongs,  and  the  ports  to  and 
from  which  she  is  bound. 

"  As  soon  as  possible  after  the  collision,  he  must 
cause  an  entry  to  be  made  in  the  log  book,  of  the 
collision  and  of  all  facts  connected  with  it." 


THI   END 


14  DAY  USE 

RETURN  TO  DESK  FROM  WHICH  BORROWED 

LOAN  DEPT. 

This  book  is  due  on  the  last  date  stamped  below,  or 

on  the  date  to  which  renewed. 

Renewed  books  are  subject  to  immediate  recall. 


12>teC)3fg 


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LD  21A-40m-4,'63 
(D6471sl0)476B 


General  Library 

University  of  California 

Berkeley 


i  \ 


M168705 


THE  UNIVERSITY  OF  CALIFORNIA  LIBRARY 


